1#include<iostream>
2#include<cmath>
3#include<iomanip>
4
5unsigned long long factorial(unsigned long long );
6
7unsigned long long factorial(unsigned long long num){
8
9 if(num<=0)
10 return 1;
11
12 return num * factorial(num-1);
13}
14
15int main()
16{
17 std::cout<<"Enter number\t"<<std::endl;
18 unsigned long long num,number;
19 std::cin >> num;
20 std::cout<<std::fixed<<std::setprecision(9)<<factorial(num)/pow(num,num)<<std::endl;
21
22}
23
24
25