#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: yangjunwen
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/