#include<iostream>
#include<iomanip>
using namespace std;
double comb[100][100];
int N;
main()
{
	cin>>N;
	comb[0][0]=1;
	for(int i=1;i<100;i++)
	{
		comb[i][0]=comb[i][i]=1;
		for(int j=1;j<i;j++)comb[i][j]=comb[i-1][j-1]+comb[i-1][j];
	}
	cout<<fixed<<setprecision(16)<<comb[N][5]/comb[99][5]*12<<endl;
}