题解 | 长椅安置

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

void solve(){
	
	int p=n;
	int c_n5=1;
	
	for(int i=p;i>=p-4;i--){
		c_n5*=i;
	}
	int five_jicheng=120;
	c_n5=c_n5/five_jicheng;
	int res=c_n5*c_n5*five_jicheng;
	
	cout<<res<<endl;
	
	return;
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	cin>>n;
	
	solve();
	
    return 0;
}