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