#include<stdio.h>
#include<ctype.h>
#include<stdlip.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 (ascii % 2 == 0)
        evenSum += ascii;
        else
        oddSum += ascii;
    }
    printf("%d\n", abs(evenSum - oddSum));
    return 0;
}