#include<bits/stdc++.h>
using namespace std;
int main()
{
	string n;
	cin>>n;
	int n2=n.size(),s=0;
	for(int i=0;i<n2;i++)
	{
		s+=n[i]-'0';
	}
	cout<<s;
}
/**************************************************************
	Problem: 1115
	User: wangyuxin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/