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;
}