#include <bits/stdc++.h>
using namespace std;
int main()
{
	char a[600];
	int i,s=0;
	cin>>a;
	for(i=0;i<=a[i]!='\0';i++)
	{
		s+=a[i]-48;
	}
	cout<<s<<endl;
	
	
	
	
	
	return 0;
}

/**************************************************************
	Problem: 1115
	User: 21A
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/