// yukicoder: No.173 カードゲーム（Medium）
// 2019.8.22 bal4u

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() { // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

double getdbl() { // 実数の入力
	int minus = 0;
	double x, y;
	int n = 0, c = gc();
	if (c == '-') minus = 1, c = gc();
	do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
	if (c == '.') {
		x = 0;
		y = 1, c = gc();
		do y *= 0.1, x += y * (c & 0xf), c = gc(); while (c >= '0');
		x += n;
	} else x = n;
	if (minus) x = -x;
	return x;
}

#define MAX 1000
#define LOOP 50000
int N;
int A[25], B[25];  // それぞれの最大値
double Pa, Pb;
int a[25], b[25];

int cmp(const void *u, const void *v) { return *(int *)u - *(int *)v; }

// 32ビット乱数を生成する
unsigned int xorshift(void) {
	static unsigned int y = 2463534242;
	y = y ^ (y << 13);
	y = y ^ (y >> 17);
	y = y ^ (y << 5);
	return y;
}

static int f[25];
void setup(int *a, int *A, double P) {
	int i, j, k; double p;
	memcpy(f, A, sizeof(f));
	for (i = 1; i < N; i++) {
		p = (xorshift() % (MAX+1)) / (double)MAX;
		if (p <= P) j = 0;
		else j = 1+(N-i)*(p-P)/(1-P);

		if (j > N-i) j = N-i;
		
		for (k = 0; k < N; k++) {
			if (f[k] && j-- == 0) {
				a[i-1] = f[k], f[k] = 0;
				break;
			}
		}
	}
	for (k = 0; k < N; k++) {
		if (f[k]) { a[N-1] = f[k]; break; }
	}
}

int main()
{
	int i, loop, sa, sb, ans;

	N = in(), Pa = getdbl(), Pb = getdbl();
	i = N; while (i--) A[i] = in();
	i = N; while (i--) B[i] = in();
	qsort(A, N, sizeof(int), cmp), qsort(B, N, sizeof(int), cmp);

	ans = 0, loop = LOOP; while (loop--) {
		sa = sb = 0;
		setup(a, A, Pa), setup(b, B, Pb);
		for (i = 0; i < N; i++) {
			int t = a[i] - b[i];
			if (t > 0) sa += a[i] + b[i];
			else if (t < 0) sb += a[i] + b[i];
		}
		if (sa > sb) ans++;
	}
	ans = (ans+50)*10000 / LOOP;
	if (ans >= 10000) puts("1.0000");
	else printf("0.%04d\n", ans);
	return 0;
}