Untitled

// Online C++ compiler to run C++ program online
#include <iostream>

int digSum(int n){
    int sum = 0;
    while(n > 0 || sum > 9){
        if(n==0){
            n = sum;
            sum = 0;
        }
        sum += n%10;
        n /= 10;
    }
    return sum;
}

int main() {
    // Write C++ code here
    int n = 12345;
    std::cout<<digSum(n);
    
    return 0;
}