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;

const auto rep = 10 ^^ 6;

void main()
{
  auto rd = readln.split;
  auto n = rd[0].to!size_t, pa = rd[1].to!real, pb = rd[2].to!real;
  auto ai = readln.split.map!(to!int).array;
  auto bi = readln.split.map!(to!int).array;

  ai.sort();
  bi.sort();

  auto r = 0;
  foreach (_; 0..rep) {
    auto wa = 0, wb = 0;
    auto aj = ai.dup, bj = bi.dup;
    foreach (i; 0..n) {
      int a = pickup(aj, pa);
      int b = pickup(bj, pb);
      if (a > b) wa += a + b;
      else wb += a + b;
    }
    if (wa > wb) r += 1;
  }

  writeln(r.to!real / rep);
}

int pickup(ref int[] ai, real p)
{
  int a;
  if (ai.length == 1 || uniform(0.0L, 1.0L) <= p) {
    a = ai.front;
    ai = ai[1..$];
  } else {
    auto i = uniform(1, ai.length);
    a = ai[i];
    ai = ai[0..i] ~ ai[i+1..ai.length];
  }
  return a;
}