#include<stdio.h>
#include<ctype.h>

int calculateDifference(char *str, int n) {
    int evenSum = 0, oddSum = 0;
    for (int i = 0; i < n; i++) {
        if (!isalpha(str[i])) {
            printf("Invalid input\n");
            return -1;
        }
        if ((int)str[i] % 2 == 0) {
            evenSum += (int)str[i];
        }else{
            oddSum += (int)str[i];
        }
    }
    return abs(evenSum - oddSum);
}
int main(){
    int n;
    scanf("%d", &n);
    
    if (n < 1 || n > 100) {
        printf("Invalid input\n");
        return 0;
    }
    
    char initials[n];
    for (int i = 0; i , n; i++) {
        scanf(" %c", &initials[i]);
    }
    int result = calculatateDifference(initials, n);
    if (result != -1) {
        printf("%d\n", result);
    }
    
    return
}