#include<bits/stdc++.h>
using namespace std;
int n;
string s;
int main(){
	cin >> n;
	cin >> s;
	int ans = 0;
	for (int i = 0; i < n; i++){
		if (s[i] >= 'a' && s[i] <= 'z') ans += s[i] - 97 + 1;			
		else if (s[i] >= 'A' && s[i] <= 'Z') ans = ans + s[i] - 65 - 65;
	}
	cout << ans;
	return 0;
}