#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,b,c,d,e;
    cin>>a;
    b=a%10;
    c=a/10%10;
    d=a/100%10;
    e=a/1000;
    cout<<b+c+d+e;
}
/**************************************************************
	Problem: 1390
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/