#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
int main()
{
    int N;
    if(scanf("%d",&N)!=1){
        printf("Invalid input");
        return 0;
    }
    if(N<0){
        printf("Invalid input");
        return 0;
    }
    char arr[100];
    char *p=arr;
    for(int i=0;i<N;i++){
        if(scanf("%c",p+i)!=1){
            printf("Invalid input");
            return 0;
        }
    }
    long long sum_evan=0,sum_odd=0;
    for (int i=0;i<N;i++){
        char ch=*(p+i);
        if(!isalpha((unsigned char)ch)){
            printf("Invalid input");
            retuurn 0;
        }
        int ascii=(int)ch;
        if(ascii%2==0){
            sum_even+=ascii;
        }else{
            sum_odd+=ascii;
        }
    }
    long long diff=llabs(sum_even-sum_odd);
    printf("%lld",diff);
    
    return 0;
}