import std.algorithm, std.array, std.container, std.range, std.bitmanip;
import std.numeric, std.math, std.bigint, std.random, core.bitop;
import std.string, std.conv, std.stdio, std.typecons;

void main()
{
  auto n = readln.chomp.to!int;
  writefln("%.9f", 4 * (3f / 4) ^^ n);
}