#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,g,s,b,q,h;
    cin>>n;
    g=n%10;
    s=n/10%10;
    b=n/100%10;
    q=n/1000;
    h=g+s+b+q;
    cout<<h;
}
/**************************************************************
	Problem: 1390
	User: panjinyan
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/