#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 arr[105];
    char *ptr = arr;
    for (int i = 0; i < N; i++){
        scanf(" %c", &arr[i]);
        
        if (!isalpha(arr[i])){
            printf("Invalid input");
            return 0;
        }
    }
    int evensum = 0, oddsum = 0;
    for (int i = 0; i < n; i++){
        int ascii = *(ptr + i);
        if (ascii % 2 == 0)
        evensum += ascii;
        else
        oddsum += ascii;
    }
    int diff = abs(evensum - oddsum);
    printf("%d", diff);
    
    return 0;
}