#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main(){
    int n;
    scanf("%d",&n);
    
    if (n < 0) {
        printf("Invalid input");
        return 0;
    }
    char ch[n];
    int even = 0, odd = 0;
    char *ptr = ch;
    
    for (int i = 0; i < n; i++) {
        scanf(" %c", ptr + i);
        if (!isalpha(*(ptr + i))) {
            printf("Invalid input");
            return 0;
        }
        int ascii = *(ptr + i);
        if (ascii % 2 == 0)
            even += ascii;
        else
        odd += ascii;
    }
    printf("%",abs(even - odd));
    return 0;
}