#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: 21A
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/