#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	cin>>n;
	int q=n/100%10;//123 1
	int d=n/10%10;//123 12
	int c=n%10;//2*10=20
	int w=n/1000;
	cout<<q+d+c+w;
	return 0;
}
/**************************************************************
	Problem: 1027
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/