TONGCS564 C++

#include <bits/stdc++.h>
using namespace std;
int n,a,b,c,d,s;
int main(){
    freopen("tongcs564.inp","r",stdin);
    freopen("tongcs564.out","w",stdout);
    cin>>n;
    d = n%10;
    n = n/10;    // n = 231
    c = n%10;
    n = n/10;    // n = 23
    b = n%10;
    n = n/10;    // n = 2
    a = n;
    s = a + b + c + d;
    cout<<s;
}