#include<stdio.h>
#include<ctype.h>
int main()
{
    int n;
    char arr[100];
    int evenSum = 0; oddSum = 0;
    
    scanf("%d",&n);
    
    if(n < 1 || n >100){
        printf("Invalid input");
        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;
}