#include<bits/stdc++.h>
using namespace std;
int main(){
	int c=0;
	string s;
	cin>>s;
	for(int i=0;i<s.size();i++){
		c=c+(s[i]-48);
	}
	cout<<c;

	return 0;
}

/**************************************************************
	Problem: 1115
	User: zhuanghaoxiang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/