#include <bits/stdc++.h>
using namespace std;
int main(){

	int i,b,c,d,x;
	cin>>i;
	b=i/100%10;
	c=i/10%10;
	d=i%10;
	x=b+c+d;
	cout<<x;
	
	return 0;
}
/**************************************************************
	Problem: 1716
	User: huangyaojie3
	Language: C++
	Result: Accepted
	Time:26 ms
	Memory:2072 kb
****************************************************************/