#include<bits/stdc++.h>
using namespace std;

int main() {
	int n, ans = 0, tmp;
	scanf("%d", &n), tmp = n;
	while(n) {
		ans += n % 10;
		n /= 10;
	}
	if(tmp % 10 == 0) printf("%d\n", ans * 10);
	else printf("%d\n", ans);
	return 0;
}