#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main()
{
    int n;
    char arr[100];
    int evenSum = 0, oddSum = 0;
    
    scanf("%d" , &n);
    
    if (n < 1 || n > 100)
    {
        printf("Invalid input\n");
        return 0;
    }
    
    for (int i = 0; i < n; i++)
    {
        scanf(" %c ", &arr[i]);
        if (!isalpha(arr[i]))
        {
            printf("Invalid input\n");
            return 0;
        }
    }
    
    char *ptr = arr;
    
    for (int i = 0; i < n; i++)
    {
        int ascii = (int)*(ptr + i);
        if (asci % 2 == 0)
           evenSum += ascii;
        else
           oddSum += ascii;
    }
    
    printf("%d\n", abs (evenSum - oddSum));
    return 0;
}