poj 2316 SPIN

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>using namespace std;string st, wheel;int main(){    getline(cin, wheel);    while (getline(cin, st) && st != "")    {        for (unsigned i = 0; i < st.length(); i++) wheel[i] = ((wheel[i] - '0') + (st[i] - '0'))%10 + '0';    }    cout << wheel << endl;    return 0;}