import std.algorithm, std.conv, std.range, std.stdio, std.string;
import std.random;    // random

const auto iter = size_t(500_000);

void main()
{
  auto n = readln.chomp.to!size_t;
  auto k = readln.chomp.to!size_t;

  auto d1 = [1, 1, 1, 1, 1, 1];
  auto d2 = [0, 0, 0, 1, 1, 1];

  auto w = size_t(0);
  foreach (_; iter.iota) {
    auto taro = chain((n - k).iota.map!(_ => dice(d1)), k.iota.map!(_ => dice(d2))).sum;
    auto jiro = n.iota.map!(_ => dice(d1)).sum;

    if (taro > jiro) ++w;
  }

  writefln("%.5g", w.to!real / iter);
}