#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,s=0,a;
	cin>>n;
	while(n!=0){
		a=n%10;
		s=s+a;
		n=n/10;
	}	
	cout<<s;

	return 0;
}

/**************************************************************
	Problem: 1115
	User: zhuanghaoxiang
	Language: C++
	Result: Wrong Answer
****************************************************************/