#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,a,b,c,d,s;
    cin>>n;
    a=n%10;
    b=n/10%10;
    c=n/100%10;
    d=n/1000;
    s=a+b+c+d;
    cout<<s;
    return 0;
}
/**************************************************************
	Problem: 1418
	User: wuzhijing
	Language: C++
	Result: Wrong Answer
****************************************************************/