#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main() {
    int n;
    scanf("%d", &n);
    
    if (n < 0 ) {
        printf("Invalid input\n");
        return 0;
    }
    
    char initials[n * 2];
    char *ptr = initials;
    int sum_even_ascii = 0;
    int sum_odd_ascii = 0;
    int i;
    
    for (i = 0; i < n; i++) {
        char c;
        scanf(" %c", &c);
        
        if (!isalpha(c)) {
            printf("Invalid input\n");
            return 0;
        }
        *ptr = c;
        ptr++;
    }
    
    ptr = initials;
    
    for (i = 0; i < n; i++) {
        if (*ptr % 2 == 0) {
            sum_even_ascii += *ptr;
        } else {
            sum_odd_ascii += *ptr;
        }
        ptr++;
    }
    printf("%d\n", abs(sum_even_ascii - sum_odd_ascii));
    
    return 0;
}