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

	return 0;
}

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