#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <complex>
#include <string.h>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <iomanip>
#include <sys/time.h>
#include <tuple>
#include <random>
using namespace std;

#define endl '\n'
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define UNIQ(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;
typedef complex<double> comp;
typedef vector< vector<ld> > matrix;
struct pairhash {
public:
    template<typename T, typename U>
    size_t operator()(const pair<T, U> &x) const {
	size_t seed = hash<T>()(x.first);
	return hash<U>()(x.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }
};
const int inf = 1e9 + 9;
const ll mod = 1e9 + 7;
const double eps = 1e-8;
const double pi = acos(-1);

int n;
double p[2];
int a[2][20];

double prob[2][1<<21];
double q[2][21][21];

int bitcount(int bits) {
    bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);
    bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);
    bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);
    bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);
    return (bits & 0x0000ffff) + (bits >>16 & 0x0000ffff);
}

double calc_prob(int s, int k) {
    if (prob[k][s] < 0) {
        double res = 0;
        if (s == 0) {
            for (int i = 0; i < n; i++) {
                res += calc_prob(1<<i, k);
            }
        } else {
            int l, c = bitcount(s);
            for (int i = 0; i < n; i++)
                if ((s>>i)&1)
                    l = i;
            for (int i = 0; i < l; i++)
                if (!((s>>i)&1))
                    res += (1.0-p[k]) * calc_prob(s|(1<<i), k) / c;
            for (int i = l+1; i < n; i++)
                res += p[k] * calc_prob(s|(1<<i), k);
        }
        prob[k][s] = res;
    }
    return prob[k][s];
}

double solve() {
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < (1<<n); j++) prob[i][j] = -1.0;
        prob[i][(1<<n)-1] = 1.0;
        calc_prob(0, i);
        sort(a[i], a[i]+n);
        reverse(a[i], a[i]+n);

        int c, l;
        for (int j = 1; j < (1<<n); j++) {
            c = bitcount(j);
            for (int k = 0; k < n; k++)
                if ((j>>k)&1)
                    l = k;
            
            if (c == 1) {
                q[i][c][l] += prob[i][j];
            } else {
                q[i][c][l] += p[i] * prob[i][j];            
                for (int k = 0; k < l; k++)
                    if ((j>>k)&1)
                        q[i][c][k] += (1.0-p[i]) * prob[i][j] / (c-1);
            }
        }
    }

    double res = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < n; j++) {
            for (int k = 0; k < n; k++) {
                if (a[0][j] > a[1][k]) {
                    res += q[0][i][j] * q[1][i][k] * (a[0][j] + a[1][k]);
                }
            }
        }
    }
    return res;
}

void input() {
    cin >> n >> p[0] >> p[1];
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < n; j++)
            cin >> a[i][j];
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);

    input();
    cout << solve() << endl;
}