#include <bits/stdc++.h>
using namespace std;
int n;
int g;
int s;
int b;
int q;
int main(){
    cin>>n;
    g=n%10;
    s=n/10%10;
    b=n/100%10;
    q=n/1000%10;
    cout<<g+s+b+q;
	return 0;
}
/**************************************************************
	Problem: 1390
	User: zengdongxin
	Language: C++
	Result: Accepted
	Time:32 ms
	Memory:2072 kb
****************************************************************/