#include <bits/stdc++.h>
#include <iomanip>
#include <functional>
#include <sstream>
#include <bit>
#include <numeric>

using namespace std;

int main() {
    int N; cin >> N;
    double PA, PB; cin >> 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];
    ranges::sort(A);
    ranges::sort(B);

    auto calc = [&](double P, vector<vector<double>>& cards) {
        // DP[ 状態S ] := 状態Sとなる確率
        // cards[n][c] := n試合目でカードcを出す確率
        vector<double> DP(1 << N);
        
        DP[(1 << N) -1] = 1.0;
        for (int s=(1<<N)-1;0<s;s--) {
            bool is_first = true;
            int rem = popcount((unsigned int)s);
            for (int c=0;c<N;c++) {
                if ((1 << c) & s) {
                    if (rem==1) {
                        double p = 1.0;
                        double px = DP[s] * p;
                        cards[N-rem][c]  += px;
                        DP[s ^ (1 << c)] += px;
                        break;
                    }
                    double p = is_first ? P : ((double)1.0 - P) / (rem-1.0);
                    is_first = false;
                    double px = DP[s] * p;
                    cards[N-rem][c]  += px;
                    DP[s ^ (1 << c)] += px;
                }
            }
        }
        cerr << "DP[0] := " << DP[0] << endl;
    };
    vector cards_a(N, vector<double>(N));
    vector cards_b(N, vector<double>(N));
    calc(PA, cards_a);
    calc(PB, cards_b);

    double res = 0;
    for (int n=0;n<N;n++)
        for (int a=0;a<N;a++)
            for (int b=0;b<N;b++) {
                if (A[a] > B[b])
                    res += (A[a] + B[b]) * (cards_a[n][a] * cards_b[n][b]);
            }
    cout << fixed << setprecision(12) << res << endl;
}