#include<bits/stdc++.h>
using namespace std;

int main(){
	int n;
	cin>>n;
	if(n>=30) printf("%.1f",1.0*n);
	else if(n>=20&&n<=29) printf("%.1f",1.2*n);
	else if(n>=10&&n<=19) printf("%.1f",1.5*n);
	else printf("%.1f",1.8*n);
	return 0;
}

/**************************************************************
	Problem: 1304
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:21 ms
	Memory:2072 kb
****************************************************************/