#include<bits/stdc++.h>
using namespace std;
string s;
int h;
int main(){
	cin>>s;
	for(int i=0;i<s.size();i++){
		h=h+(s[i]-'0');
	}
	cout<<h;
	return 0;
}

/**************************************************************
	Problem: 1115
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/