#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

int main() {
	int N;
	double P[2];
	scanf("%d%lf%lf", &N, &P[0], &P[1]);
	vector<int> A[2];
	rep(k, 2) A[k].resize(N);
	rep(i, N) scanf("%d", &A[0][i]);
	rep(i, N) scanf("%d", &A[1][i]);
	vector<vector<double> > prob[2];
	rep(k, 2) {
		sort(all(A[k]));
		prob[k].assign(N, vector<double>(N, 0.));
		vector<vector<double> > &v = prob[k];
		double Q = P[k];
		vector<double> dp(1 << N, 0);
		dp[(1 << N)-1] = 1;
		for(int i = (1 << N)-1; i > 0; -- i) {
			double x = dp[i];
			if(x < 1e-100) continue;
			int p = N, q = -1;
			rep(j, N) if(i >> j & 1) {
				-- p;
				if(q == -1) q = j;
			}
			if(i == (1 << q)) {
				dp[0] += x;
				v[p][q] += x;
			}else {
				dp[i & ~(1 << q)] += x * Q;
				v[p][q] += x * Q;
				double y = x * (1-Q) / (N - 1 - p);
				reu(j, q+1, N) if(i >> j & 1) {
					dp[i & ~(1 << j)] += y;
					v[p][j] += y;
				}
			}
		}
//		rep(i, N) rep(j, N)
//			cerr << k << ", " << i << ", " << j << ": " << v[j][i] << endl;
	}
	double ans = 0;
	rep(i, N) {
		rep(j, N) if(A[0][i] > A[1][j]) {
			double p = 0;
			rep(k, N) p += prob[0][k][i] * prob[1][k][j];
			ans += p * (A[0][i] + A[1][j]);
		}
	}
	printf("%.12f\n", ans);
	return 0;
}