poj1519

It did not take into account large numbers, wa, and then enter into a string, and then one by one into int sum

#include<iostream>
using namespace std;
int main(void)
{
    string s;
    int sum;
    while(cin>>s&&((int)s[0]-48!=0))
    {
       int m=0;
       for(int i=0;i<s.size();i++)
       {
           m+=(int)s[i]-48;
       }
       while(m>=10)
        {   sum=0;
            while(m)
            {
                sum+=m%10;
                m=m/10;
            }
            m=sum;
        }
        cout<<m<<endl;
    }
    return 0;
}