#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main() {
    int n;
    char arr[100];
    int evnsum = 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)
        evnsum += ascii;
        else
        oddsum += ascii;
    }
    printf("%d\n" , abs(evensum - oddsum));
    return 0;
}