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.regex, std.conv, std.stdio, std.typecons; void main() { auto rd = readln.split; auto n = rd[0].to!int, p = rd[1].to!real; auto ri = new real[](n + 1); foreach (i; 2..n + 1) { auto d = divisors(i).length; if (d == 0) ri[i] = 1; else ri[i] = (1 - p) ^^ d; } writefln("%.7f", ri[2..$].sum); } int[] divisors(int n) { int[] ri; auto limit = n.to!real.sqrt.to!int; foreach (d; 2..limit + 1) { if (n % d == 0) { if (n == d * d) ri ~= d; else ri ~= [d, n / d]; } } return ri; }