#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	cin>>n;
	if(n<=10){
		cout<<fixed<<setprecision(2)<<n*0.8+0.2;
	}
	if(n>10&&n<=20){
		n=n-10;
		cout<<fixed<<setprecision(2)<<n*0.75+8.2;
	}
	if(n>20&&n<=30){
		n=n-20;
		cout<<fixed<<setprecision(2)<<n*0.7+15.7;
	}
	if(n>30){
		cout<<"Fail";
	}
	return 0;
}