#include<bits/stdc++.h>
using namespace std;
int main()
{
	string n;
	cin>>n;
	int z=0;
	int a=n.size();
	for(int i=0;i<a;i++)
	{
		z+=n[i]-48;
	}
	cout<<z;
	return 0;
} 
/**************************************************************
	Problem: 1115
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2076 kb
****************************************************************/