Problem:
Score : 300 points

Problem Statement

We have two permutations P and Q of size N (that is, P and Q are both rearrangements of (1,~2,~...,~N)).

There are N! possible permutations of size N. Among them, let P and Q be the a-th and b-th lexicographically smallest permutations, respectively. Find |a - b|.

Notes

For two sequences X and Y, X is said to be lexicographically smaller than Y if and only if there exists an integer k such that X_i = Y_i~(1 \leq i < k) and X_k < Y_k.

Constraints

2 \leq N \leq 8

P and Q are permutations of size N.

Input

Input is given from Standard Input in the following format:

N
P_1 P_2 ... P_N
Q_1 Q_2 ... Q_N

Output

Print |a - b|.

Sample Input 1

3
1 3 2
3 1 2

Sample Output 1

3

There are 6 permutations of size 3: (1,~2,~3), (1,~3,~2), (2,~1,~3), (2,~3,~1), (3,~1,~2), and (3,~2,~1). Among them, (1,~3,~2) and (3,~1,~2) come 2-nd and 5-th in lexicographical order, so the answer is |2 - 5| = 3.

Sample Input 2

8
7 3 5 4 2 1 6 8
3 8 2 5 4 6 7 1

Sample Output 2

17517

Sample Input 3

3
1 2 3
1 2 3

Sample Output 3

0

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;
public class Main {

    public static int fact(int n){
        int ans = 1;
        while(n != 0){
            ans *= n;
            n--;
        }
        return ans;
    }

    public static int func(int[] a,int num){
        int ans = 0;
        for(int i = 0; i < a.length ; i++){
            ans += fact(num-i)*(a[i]-1);
        }
        return ans;
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int in_num = Integer.parseInt(sc.next());
        int[] p = new int[in_num];
        int[] q = new int[in_num];
        for(int i = 0 ; i < in_num ; i++){
            p[i] = Integer.parseInt(sc.next());
        }
        for(int i = 0 ; i < in_num ; i++){
            q[i] = Integer.parseInt(sc.next());
        }
        System.out.println(Math.abs(func(p,in_num)-func(q,in_num)));
    }
}