---
title: S1A 數字和
tags: solution
---

# A. 數字和

- 本題源自於Online Judge(UVa)：[11332 - Summing Digits](https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2307)

#include <iostream>
using namespace std;

long f(long x){
    long sum1=0;

    while(x > 0) {
        sum1 += x%10;
        x /= 10;
    }

    return sum1;
}

int main() {
    long num;

    while (cin >> num && num != 0) {
        while ((num = f(num))>=10);
        cout << num << "\n";
    }
}