AC题解

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

signed main() {
    int n;
    cin >> n;
    
    vector<int> cows(n);
    for (int i = 0; i < n; ++i) {
        cin >> cows[i];
    }
    
    vector<int> stalls(n);
    for (int i = 0; i < n; ++i) {
        cin >> stalls[i];
    }

    sort(cows.begin(), cows.end());
    sort(stalls.begin(), stalls.end());
    vector<int> possible_places(n, 0);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (cows[i] <= stalls[j]) {
                possible_places[i] += 1;
            }
        }
    }
    int product = 1;
    for (int i = n - 1; i >= 0; --i) {
        product *= possible_places[i] - (n - i - 1);
    }

    cout << product << endl;

    return 0;
}