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

/**************************************************************
	Problem: 1115
	User: zhouhongyi
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2076 kb
****************************************************************/