#include<stdio.h>
#include<ctype.h>
int main()
{
    int N;
    scanf("%d", &N);
    if(N <= 0 || N> 100){
        printf("Invalid input");
        return 0;
    }
    char c;
    int evenSum = 0, oddSum = 0;
    for(int i = 0;i < N; i++){
        scanf("%c", &c);
        if(!isalpha((unsigned char)c)){
            printf("Invalid input");
            return 0;
        }
        
        if(c % 2 == 0)
          evenSum += c;
        else
          oddSum += c;
    }
    printf("%d", abs(evenSum - oddSum));
return 0;
}