#include<bits/stdc++.h>
using namespace std;
int main(){
	float n;
	cin>>n; 
	if(n<=10) printf("2.50\n");
	else{
		n=2.50+1.50*(n-10);
		printf("%.2f\n",n);
	}
	return 0;	
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
float a;
cin>>a; 
if(a<=10)
printf("2.50\n");
else{
a=2.50+1.50*(a-10);
printf("%.2f\n",a);
}
}