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

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