#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,g,s,b,q,h;
	cin>>a;
	g=a%10;
	s=a/10%10;
	b=a/100%10;
	q=a/1000;
	h=g+s+b+q;
	cout<<h;
	return 0;
}

/**************************************************************
	Problem: 1390
	User: chenjunlin
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/