#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);
}
/**************************************************************
	Problem: 1304
	User: caiqiaoxi
	Language: C++
	Result: Accepted
	Time:23 ms
	Memory:2072 kb
****************************************************************/