#include<bits/stdc++.h>
using namespace std;
int main(){
	string a;
	int v=0;
	cin>>a;
	for(int i=0;i<a.size();i++){
		v=v+a[i]-48;
	}
	cout<<v;
	return 0;
}
/**************************************************************
	Problem: 1115
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/