import std.stdio, std.string, std.conv; import std.range, std.algorithm, std.array, std.typecons, std.container; import std.math, std.numeric, core.bitop; void main() { int n; scan(n); if (n < 6) { writeln(0); return; } real ans = 1; ans -= 6 * (5.0 / 6.0)^^n; ans += 15 * (4.0 / 6.0)^^n; ans -= 20 * (3.0 / 6.0)^^n; ans += 15 * (2.0 / 6.0)^^n; ans -= 6 * (1.0 / 6.0)^^n; writefln("%.12f", ans); } void scan(T...)(ref T args) { import std.stdio : readln; import std.algorithm : splitter; import std.conv : to; import std.range.primitives; auto line = readln().splitter(); foreach (ref arg; args) { arg = line.front.to!(typeof(arg)); line.popFront(); } assert(line.empty); } void fillAll(R, T)(ref R arr, T value) { static if (is(typeof(arr[] = value))) { arr[] = value; } else { foreach (ref e; arr) { fillAll(e, value); } } }