#include <bits/stdc++.h>
using namespace std;

const int MOD = 1e9 + 7;

struct con{
    int h, t;
    bool operator<(const con& other) const {
        if (h != other.h) return h < other.h;
        return t < other.t; 
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int N;cin >> N;
    vector<con> all;
    for (int i = 0; i < N + 1; ++i) {
        int h;cin >> h;
        all.push_back({h, 1});
    }
    for (int i = 0; i < N; ++i) {
        int h;
        cin >> h;
        all.push_back({h, 0});
    }
    sort(all.begin(), all.end());

    vector<long long> dp(N + 2, 0);
    dp[0] = 1;

    for (const auto& person : all) {
        vector<long long> next_dp(N + 2, 0);
        if (person.t == 1) { 
            for (int j = 0; j <= N; ++j) {
                if (dp[j] == 0) continue;
                next_dp[j + 1] = (next_dp[j + 1] + dp[j] * (j + 1)) % MOD;
            }
        } else { 
            for (int j = 2; j <= N + 1; ++j) {
                if (dp[j] == 0) continue;
                next_dp[j - 1] = (next_dp[j - 1] + dp[j] * (j - 1)) % MOD;
            }
        }
        dp = move(next_dp);
    }

    cout << dp[1] << endl;

    return 0;
}