#include <iostream>
#include <cmath>
using namespace std;
int main() {
    int a;
    cin>>a;
    int b=a%10;
    int e=a/1000;
    int d=a/100-10*e;
    int c=a/10-100*e-10*d;
    int f=b+c+d+e;
    cout<<f;
    return 0;
}