OJ Board

I found my mistake !!

Why this code generate WA ,could anybody give some test cases?

#include<cstdio>
#include<string>
#include<iostream>
#define mod 131071
using namespace std;

void doit(string s){
int sol=0;
for(int i=0;i<s.length();i++){
sol*=2;
sol%=mod;
sol=(sol+(int)(s[i]-'0'))%mod;
}
sol%=mod;
if(sol ...