#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 (ascii % 2 == 0)
    evensum += ascii;
    else
    oddsum += ascii;
}

printf("%d\n", abs(evensum - oddsum));

return 0;
}