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

/**************************************************************
	Problem: 1002
	User: miaozeyu
	Language: C++
	Result: Wrong Answer
****************************************************************/