#include <stdio.h>
#include <stdlib.h>
#include <memory.h>

typedef struct
{
	unsigned int count[2];
	unsigned int state[4];
	unsigned char buffer[64];   
}MD5_CTX;
 
						 
#define F(x,y,z) ((x & y) | (~x & z))
#define G(x,y,z) ((x & z) | (y & ~z))
#define H(x,y,z) (x^y^z)
#define I(x,y,z) (y ^ (x | ~z))
#define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n)))
#define FF(a,b,c,d,x,s,ac) \
		  { \
		  a += F(b,c,d) + x + ac; \
		  a = ROTATE_LEFT(a,s); \
		  a += b; \
		  }
#define GG(a,b,c,d,x,s,ac) \
		  { \
		  a += G(b,c,d) + x + ac; \
		  a = ROTATE_LEFT(a,s); \
		  a += b; \
		  }
#define HH(a,b,c,d,x,s,ac) \
		  { \
		  a += H(b,c,d) + x + ac; \
		  a = ROTATE_LEFT(a,s); \
		  a += b; \
		  }
#define II(a,b,c,d,x,s,ac) \
		  { \
		  a += I(b,c,d) + x + ac; \
		  a = ROTATE_LEFT(a,s); \
		  a += b; \
		  }                                            
void MD5Init(MD5_CTX *context);
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen);
void MD5Final(MD5_CTX *context,unsigned char digest[16]);
void MD5Transform(unsigned int state[4],unsigned char block[64]);
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len);
  
unsigned char PADDING[]={0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
						 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
						 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
						 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
						 
void MD5Init(MD5_CTX *context)
{
	 context->count[0] = 0;
	 context->count[1] = 0;
	 context->state[0] = 0x67452301;
	 context->state[1] = 0xEFCDAB89;
	 context->state[2] = 0x98BADCFE;
	 context->state[3] = 0x10325476;
}
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen)
{
	unsigned int i = 0,index = 0,partlen = 0;
	index = (context->count[0] >> 3) & 0x3F;
	partlen = 64 - index;
	context->count[0] += inputlen << 3;
	if(context->count[0] < (inputlen << 3))
	   context->count[1]++;
	context->count[1] += inputlen >> 29;
	
	if(inputlen >= partlen)
	{
	   memcpy(&context->buffer[index],input,partlen);
	   MD5Transform(context->state,context->buffer);
	   for(i = partlen;i+64 <= inputlen;i+=64)
		   MD5Transform(context->state,&input[i]);
	   index = 0;        
	}  
	else
	{
		i = 0;
	}
	memcpy(&context->buffer[index],&input[i],inputlen-i);
}
void MD5Final(MD5_CTX *context,unsigned char digest[16])
{
	unsigned int index = 0,padlen = 0;
	unsigned char bits[8];
	index = (context->count[0] >> 3) & 0x3F;
	padlen = (index < 56)?(56-index):(120-index);
	MD5Encode(bits,context->count,8);
	MD5Update(context,PADDING,padlen);
	MD5Update(context,bits,8);
	MD5Encode(digest,context->state,16);
}
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len)
{
	unsigned int i = 0,j = 0;
	while(j < len)
	{
		 output[j] = input[i] & 0xFF;  
		 output[j+1] = (input[i] >> 8) & 0xFF;
		 output[j+2] = (input[i] >> 16) & 0xFF;
		 output[j+3] = (input[i] >> 24) & 0xFF;
		 i++;
		 j+=4;
	}
}
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len)
{
	 unsigned int i = 0,j = 0;
	 while(j < len)
	 {
		   output[i] = (input[j]) |
					   (input[j+1] << 8) |
					   (input[j+2] << 16) |
					   (input[j+3] << 24);
		   i++;
		   j+=4; 
	 }
}
void MD5Transform(unsigned int state[4],unsigned char block[64])
{
	 unsigned int a = state[0];
	 unsigned int b = state[1];
	 unsigned int c = state[2];
	 unsigned int d = state[3];
	 unsigned int x[64];
	 MD5Decode(x,block,64);
	 FF(a, b, c, d, x[ 0], 7, 0xd76aa478);  
 FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);  
 FF(c, d, a, b, x[ 2], 17, 0x242070db);  
 FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);  
 FF(a, b, c, d, x[ 4], 7, 0xf57c0faf);  
 FF(d, a, b, c, x[ 5], 12, 0x4787c62a);  
 FF(c, d, a, b, x[ 6], 17, 0xa8304613);  
 FF(b, c, d, a, x[ 7], 22, 0xfd469501);  
 FF(a, b, c, d, x[ 8], 7, 0x698098d8);  
 FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);  
 FF(c, d, a, b, x[10], 17, 0xffff5bb1);  
 FF(b, c, d, a, x[11], 22, 0x895cd7be);  
 FF(a, b, c, d, x[12], 7, 0x6b901122);  
 FF(d, a, b, c, x[13], 12, 0xfd987193);  
 FF(c, d, a, b, x[14], 17, 0xa679438e);  
 FF(b, c, d, a, x[15], 22, 0x49b40821);  
 
  
 GG(a, b, c, d, x[ 1], 5, 0xf61e2562);  
 GG(d, a, b, c, x[ 6], 9, 0xc040b340);  
 GG(c, d, a, b, x[11], 14, 0x265e5a51);  
 GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);  
 GG(a, b, c, d, x[ 5], 5, 0xd62f105d);  
 GG(d, a, b, c, x[10], 9,  0x2441453);  
 GG(c, d, a, b, x[15], 14, 0xd8a1e681);  
 GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);  
 GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);  
 GG(d, a, b, c, x[14], 9, 0xc33707d6);  
 GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);  
 GG(b, c, d, a, x[ 8], 20, 0x455a14ed);  
 GG(a, b, c, d, x[13], 5, 0xa9e3e905);  
 GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);  
 GG(c, d, a, b, x[ 7], 14, 0x676f02d9);  
 GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);  
 
  
 HH(a, b, c, d, x[ 5], 4, 0xfffa3942);  
 HH(d, a, b, c, x[ 8], 11, 0x8771f681);  
 HH(c, d, a, b, x[11], 16, 0x6d9d6122);  
 HH(b, c, d, a, x[14], 23, 0xfde5380c);  
 HH(a, b, c, d, x[ 1], 4, 0xa4beea44);  
 HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);  
 HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);  
 HH(b, c, d, a, x[10], 23, 0xbebfbc70);  
 HH(a, b, c, d, x[13], 4, 0x289b7ec6);  
 HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);  
 HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);  
 HH(b, c, d, a, x[ 6], 23,  0x4881d05);  
 HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);  
 HH(d, a, b, c, x[12], 11, 0xe6db99e5);  
 HH(c, d, a, b, x[15], 16, 0x1fa27cf8);  
 HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);  
 
  
 II(a, b, c, d, x[ 0], 6, 0xf4292244);  
 II(d, a, b, c, x[ 7], 10, 0x432aff97);  
 II(c, d, a, b, x[14], 15, 0xab9423a7);  
 II(b, c, d, a, x[ 5], 21, 0xfc93a039);  
 II(a, b, c, d, x[12], 6, 0x655b59c3);  
 II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);  
 II(c, d, a, b, x[10], 15, 0xffeff47d);  
 II(b, c, d, a, x[ 1], 21, 0x85845dd1);  
 II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);  
 II(d, a, b, c, x[15], 10, 0xfe2ce6e0);  
 II(c, d, a, b, x[ 6], 15, 0xa3014314);  
 II(b, c, d, a, x[13], 21, 0x4e0811a1);  
 II(a, b, c, d, x[ 4], 6, 0xf7537e82);  
 II(d, a, b, c, x[11], 10, 0xbd3af235);  
 II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);  
 II(b, c, d, a, x[ 9], 21, 0xeb86d391);  
	 state[0] += a;
	 state[1] += b;
	 state[2] += c;
	 state[3] += d;
}

unsigned char s[20], e[20], t[20];
int dfs(int x, int l) {
	{
		MD5_CTX md5;
		MD5Init(&md5);              
		MD5Update(&md5, s, strlen((char *)s));
		MD5Final(&md5, e);
		if (strcmp((char *)e, (char *)t) == 0) {
			return 1;
		}        
	}
	if (x == l) {
		return 0;
	}
	for (s[x] = 32; s[x] <= 126; s[x]++) {  
		if (dfs(x + 1, l)) {
			return 1;
		}
	}
	s[x] = 0;
	return 0;
}

void cases(int length) {
	int i, tmp;
	for (i = 0; i < 16; i++) {
		scanf("%2x", &tmp);
		t[i] = tmp;
	}
	dfs(0, length);
	printf("%s\n", s);

}
 
int main(int argc, char *argv[])
{

	int i;
	unsigned char example[] = "ab";
	MD5_CTX md5;
	MD5Init(&md5);
	MD5Update(&md5, example, strlen((char *)example));
	MD5Final(&md5, e);
	for (i = 0; i < 16; i++) {
 
	} 
 

	cases(11);
	 
	cases(11);
	 
	cases(11);
	 
	cases(11);
	 
	cases(11);
	cases(11);
	cases(11);
	cases(11);
	 
	cases(7);
	 
	cases(11);
	 
	return 0;
}