#include<bits/stdc++.h>
using namespace std;
int main()
{
    int a;
    float q;
    cin >> a;
    if(a < 28)
    {
        q = a * 1.68;
    }
    else
    {
        q = a * 1.98;
    }
    cout << fixed << setprecision(2) << q << endl;
    return 0;
}
/**************************************************************
	Problem: 1643
	User: fuhoubin
	Language: C++
	Result: Wrong Answer
****************************************************************/