#include<bits/stdc++.h>
using namespace std;
int s1=0;
int zhi(char a)
{
	if(a>='a'&&a<='z') s1+=(a-'a'+1);
	if(a>='A'&&a<='Z') s1-=int(a);
}
int main()
{
	int x,s=1;
	char a;
	cin>>x;
	do
	{
		cin>>a;
		s++;
		zhi(a);
	}
	while(s<x)
	;{
		cin>>a;
		s++;
		zhi(a);
	}
	cout<<s1;
	return 0;
}