#include<bits/stdc++.h>
using namespace std; 
char b[100010];
int main(){
	int a,num=0;
	scanf("%d",&a);
	for(int i=1;i<=a;i++){
		scanf("%c",&b[i]);
		if(b[i]>='a'&&b[i]<='z')num+=b[i]-83;
		else num-=b[i];
	}
	printf("%d",num);
	return 0;
}