#include <bits/stdc++.h>

using namespace std;

#define int long long

signed main()
{
	double n;
	cin >> n;
	if(n<=20)
	{
		cout << fixed << setprecision(2);
		cout << n*1.68;
	}
	if(n>20)
	{
		cout << fixed << setprecision(2);
		cout << n*1.98;
	}
	return 0;
}