#include <stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main(){
    int N,i;
    if (scanf("%d",&N) !=1 || N<0){
        printf("Invalid input");
        return 0;
    }
    char ch;
    int evenSum=0,oddSum=0;
    for(i=0;i<N;i++){
        if(scanf(" %c",&ch) !=1 || !isalpha((unsigned char)ch)){
            printf("Invalid input");
            return 0;
        }
        int ascii = (int)&ch;
        if(ascii%2==0)
          evenSum +=ascii;
        else
          oddSum +=ascii;
          
        }
        printf("%d",abs(evenSum-oddSum));
        return 0;
}