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

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