#include<iostream>
#include<cstring>
#include<vector>
#include<cmath>
using namespace std;
typedef long long int LL;
int main(){
	int n;
	int s=0;
	cin>>n;
	for(;n>0;n/=10){
		s+=n%10;
	}
	if(s==1)s=10;
	cout<<s<<endl;
	return 0;
}
