include <bits/stdc++.h>

using namespace std;

int main() {

double w;
int x;
cin >> w ;
w = ceil(w);

if (w < 5) {
	x=w * 5;

} else if (5 <= w && w < 10) {
x= w * 4;

} else if (10 <= w && w < 15) {
	x= w * 3;

} else {
	x = w * 2;

}

cout << x;

return 0;

}