#include <bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,s;
	cin>>s;
	a=s%10;
	b=s/10%10;
	c=s/100%10;
	d=s/1000;
	s=a+b+c+d;
	cout<<s;
	return 0;
}
/**************************************************************
	Problem: 1390
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/