#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
int g=n%10;
int s=n/10%10;
int b=n/100%10;
int q=n/1000;
int d=g+s+b+q;
    cout<<d;
     
     
     
return 0;
}
/**************************************************************
	Problem: 1390
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/