#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
    else
    oddsum +=ascii;
}
printf("%d\n", abs(evensum - oddsum));
return 0;
}