#include<bits/stdc++.h>
using namespace std;
int main()
{
	int sum=0;
	char m[21];
	cin>>m;
	for(int i=0;i<strlen(m);i++)
	{
		sum+=m[i]-'0'; 
	}
	cout<<sum;
	return 0;
}

/**************************************************************
	Problem: 1182
	User: lzc
	Language: C++
	Result: Wrong Answer
****************************************************************/