Задача C

#include <bits/stdc++.h>
 
using namespace std;
 
const int64_t MOD = 1e9 + 7;
 
int64_t bpow_bitwise(int64_t x, int64_t y) {
    int64_t z = 1;
    while (y > 0) {
        if (y & 1)
            z = (z * x) % MOD;
        x = (x * x) % MOD;
        y = y >> 1;
    }
    return z;
}
 
int64_t inverse(int64_t x) {
    return bpow_bitwise(x, MOD - 2);
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
 
    int64_t n;
    cin >> n;
    int fact[n + 1];
    fact[1] = 1;
    for (int64_t i = 2; i <= n - 1; ++i)
        fact[i] = (fact[i - 1] * i) % MOD;
    cout << (fact[n - 1] * inverse(2)) % MOD;
}