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 C++ (GCC 9.2.1) (judge verdict: Accepted)

#define rep(i, n) for (int i = 0; i < (n); i++)
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int MOD = 1000000007;
// MAX int 2,147,483,647 -> 10桁
// MAX ll 9,223,372,036,854,775,807 -> 19桁
// MAX O(n) 10^8 -> 8回
// double pi = M_PI or acos(-1)
// printf("%.10f\n", ans);

int main() {
    int n;
    cin >> n;
    vector<int> p(n), q(n);
    rep(i, n) cin >> p.at(i);
    rep(i, n) cin >> q.at(i);

    vector<int> oneCase(0);
    rep(i, n) oneCase.push_back(i + 1);

    int a, b, index = 1;
    do {
        if (equal(begin(oneCase), end(oneCase), begin(p), end(p))) {
            a = index;
        }
        if (equal(begin(oneCase), end(oneCase), begin(q), end(q))) {
            b = index;
        }
        index++;
    } while (next_permutation(oneCase.begin(), oneCase.end()));

    int ans = abs(a - b);

    cout << ans << endl;

    return 0;
}