#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i=0,v=0,z=0,s=0;
	cin>>n;
		i=n%10;
		v=n%100/10;
		z=n%1000/100;
		s=i+v+z;
    	cout<<s;
    }

/**************************************************************
	Problem: 1716
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2072 kb
****************************************************************/