這題鐵定要用string讀

附上大數mod函數(超好用,我用他拿AC,340KB)

int mod(string num, int a)
{
    // Initialize result
    int res = 0;

    // One by one process all digits of 'num'
    for (int i = 0; i < num.length(); i++)
         res = (res*10 + (int)num[i] - '0') %a;
 
    return res;
}

祝大家解題順利!!!