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