#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    float q;
    cin>>n;
    if(n>=30){
    	q=n*1;
    }else if(n<=29&&n>=20){
    	q=n*1.2;
    }else if(n<=19&&n>=10){
    	q=n*1.5;
    }else{
    	q=n*1.8;
    }
    printf("%.1f",q);
    return 0;
}
/**************************************************************
	Problem: 1304
	User: HUANGYIBO
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2072 kb
****************************************************************/