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

    
}