#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i,t,h;
	cin>>n;
	while(i!=0){
		t=n%i;
		h=h+t;
		i=n;
		n=n%10;
	}
	cout<<h;
}


/**************************************************************
	Problem: 1119
	User: fandaohan
	Language: C++
	Result: Wrong Answer
****************************************************************/