#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	double s;
    cin>>n;
    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("%.1lf",s);
	return 0;
}

/**************************************************************
	Problem: 1304
	User: chenzelin
	Language: C++
	Result: Accepted
	Time:33 ms
	Memory:2072 kb
****************************************************************/