import java.io.OutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Scanner; /** * Built using CHelper plug-in * Actual solution is at the top */ public class Main { public static void main(String[] args) { InputStream inputStream = System.in; OutputStream outputStream = System.out; Scanner in = new Scanner(inputStream); PrintWriter out = new PrintWriter(outputStream); Yukicoder solver = new Yukicoder(); solver.solve(1, in, out); out.close(); } static class Yukicoder { public void solve(int testNumber, Scanner in, PrintWriter out) { out.println(in.nextInt() * 3.5); } } }