OJ Board

I've solved the equation in the problem

But I still got Wrong Answer

Could anyone give me some hint????

But I couldn't agree with you.
I read the problem carefully, I think you must change all the letter in every step. ("Direct derivation from string u1 to u2 consists of replacing each occurrence of the symbol x in u1 by the string on the right side of the production for that symbol. ")
I got some ...

I checked my program but found no big mistakes. Could anyone come into help?
#include <fstream.h>
#include <string.h>

#define fin cin

bool flag[65536];
char u[20],v[20],w[20],z[20];
int tar,lz,lw;

int str2int(char *s,int len)
{
int i,ans(1);
for (i=0;i<len;i++)
if (s =='a')
ans = ans<<1 ...

Change "int" to "unsigned", and you'll get it.
There're 15 numbers totally instead of 11.