#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	float s;
	if(n>=30) s=n*1.0;
	else if(n>=20&&n<=29) s=n*1.2;
	else if(n>=10&&n<=19) s=n*1.5;
	else s=n*1.8;
	printf("%.1f",s);
}
/**************************************************************
	Problem: 1304
	User: fandaohan
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2072 kb
****************************************************************/