#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	float h;
	cin>>n;
	if(n>=30){
		h=1.0*n;
		printf("%.1f",h);
	}else if(n>=20){
		h=1.2*n;
		printf("%.1f",h);
	}else if(n>=10){
		h=1.5*n;
		printf("%.1f",h);
	}else{
		h=1.8*n;
		printf("%.1f",h);
    }
}
	
/**************************************************************
	Problem: 1304
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/