#include <ctype.h>
#include <stdlib.h>


int main() {
    int n;
    char ar[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;
}
}