#include<stdio.h>
#include<ctype.h>
#include<string.h>
int main(){
    int n;
    char arr[100];
    int evenSum=0,oddSum=0;
    scanf("%d",&n);
    if(n<1 || n>100){
        printf("Invaled input");
        return 0;
    }
    for(int i=0;i<n;i++){
        scanf(" %c",&arr[i]);
        if(!isalpha(arr[i])){
            printf("Invalid input\n");
            return 0;
        }
    }
    char *ptr = arr;
    for(int i=0;i<n;i++){
        int ascii=(int)*(ptr+i);
        if(ascii%2 == 0)
           evenSum += ascii;
        else
           oddSum += ascii; 
    }
    printf("%d\n", abs(evenSum - oddSum));
    return 0;
}