#include<stdio.h>
#include<ctype.h>
int main(){
    int N;
    if(N < 0){
        printf("Invalid input");
        return 0;
    }
    char arr[200];
    int evenSum = 0, oddSum = 0;
    for(int i = 0;i < N; i++){
        scanf("%c",(arr + i));
        if(!isalpha(*(arr + i))){
            printf("Invalid input");
            return 0;
        }
        int ascii =*(arr + i);
        if(ascii % 2 == 0)
          evenSum += ascii;
        else
          oddSum += ascii;
    }
    printf("%d", abs(evenSum - oddSum));
return 0;
}