#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main(){
    int n,i;
    char ch;
    int evenSum=0,oddSum=0;
    scanf("%d",&n);
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    for(int i=0;i<n;i++){
        scanf("%c",&ch);
        if(!isalpha(ch)){
            printf("Invalid input");
            return 0;
        }
        int*ptr=(int*)&ch;
        int ascii=*ptr;
        if(ascii%2==0)
        evenSum+=ascii;
        else
        oddSum+=ascii;
        printf("%d",abs(evenSum-oddSum));
        return 0;
    }