大数求余

#include<iostream>  
#include<cstring>  
using namespace std;  
int main()  
{  
    char str[1234];  
    int s,len,sum;  
    while(cin>>str>>s)  
    {  
        len=strlen(str);  
        sum=0;  
        for(int i=0;i<len;i++)  
        sum=(sum*10+(str[i]-'0')%s)%s;  
        cout<<sum<<endl;
    }  
}