module main;
// https://mayokoex.hatenablog.com/entry/2015/03/27/142127 より
// モンテカルロ法
import std;

alias P = Tuple!(int, int);
immutable repeatCount = 10_000;
int N;
int[] A, B;
uint PA, PB;

bool win()
{
	int aPoint = 0, bPoint = 0;
	auto aRest = [true].replicate(N), bRest = [true].replicate(N);
	foreach (i; 0 .. N - 1) {
		P[] a, b;
		foreach (j; 0 .. N) {
			if (aRest[j]) a ~= P(A[j], j);
			if (bRest[j]) b ~= P(B[j], j);
		}
		a.sort;
		b.sort;
		int aCard, bCard;
		if (uniform!"[]"(0, 1000) <= PA) {
			aCard = a[0][0];
			aRest[a[0][1]] = false;
		} else {
			int tmp = uniform!"[]"(1, N - i - 1);
			aCard = a[tmp][0];
			aRest[a[tmp][1]] = false;
		}
		if (uniform!"[]"(0, 1000) <= PB) {
			bCard = b[0][0];
			bRest[b[0][1]] = false;
		} else {
			int tmp = uniform!"[]"(1, N - i - 1);
			bCard = b[tmp][0];
			bRest[b[tmp][1]] = false;
		}
		if (aCard > bCard) aPoint += aCard + bCard;
		else bPoint += aCard + bCard;
	}
	int a, b;
	foreach (i; 0 .. N) {
		if (aRest[i]) a = A[i];
		if (bRest[i]) b = B[i];
	}
	if (a > b) aPoint += a + b;
	else bPoint += a + b;
	return aPoint > bPoint;
}

void main()
{
	// 入力
	double[2] P;
	readln.chomp.formattedRead("%d %f %f", N, P[0], P[1]);
	PA = round(P[0] * 1000).to!uint;
	PB = round(P[1] * 1000).to!uint;
	A = readln.split.to!(int[]);
	B = readln.split.to!(int[]);
	// 答えの計算
	int winNum = 0;
	foreach (_; 0 .. repeatCount) {
		winNum += win();
	}
	double ans = winNum;
	ans /= repeatCount;
	// 答えの出力
	writefln("%.10f", ans);
}