class Solution {
public:

    int add(int num){
        int ans = 0;
        while(num > 0){
            ans += num%10;
            num /= 10;
        }
        return ans;
    }

    int addDigits(int num) {
        queue<int> q;

        while(num >= 10){
            num = add(num);
        }

        return num;
    }
};