#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;
int INF = INT_MAX / 2;

vector<vector<double> > calc(int N, double p) {
	double q = 1 - p;
	vector<vector<double> > a(N, vector<double>(N));
	for (int i = 0; i < N; i++) {
		vector<double> dp(N);
		dp[i] = 1;
		for (int t = 0; t < N - 1; t++) {
			vector<double> _dp(N);
			a[i][t] += dp[0] * p;
			_dp[0] += dp[0] * q;
			for (int j = 1; j < N; j++) {
				a[i][t] += dp[j] * q / (N - t - 1);
				_dp[j - 1] += dp[j] * (p + q * (j - 1) / (N - t - 1));
				_dp[j] += dp[j] * q * (N - t - 1 - j) / (N - t - 1);
			}
			dp = _dp;
		}
		a[i][N - 1] += dp[0];
	}
	return a;
}

int main() {
	int N; double PA, PB; cin >> N >> PA >> PB;
	vector<int> A(N), B(N);
	for (int i = 0; i < N; i++)
		cin >> A[i];
	for (int i = 0; i < N; i++)
		cin >> B[i];
	sort(A.begin(), A.end());
	sort(B.begin(), B.end());
	vector<vector<double> > a = calc(N, PA), b = calc(N, PB);
	double e = 0;
	for (int i = 0; i < N; i++)
		for (int j = 0; j < N; j++)
			if (A[i] > B[j])
				for (int t = 0; t < N; t++)
					e += (A[i] + B[j]) * a[i][t] * b[j][t];
	printf("%.10f\n", e);
}