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