#include <iostream>
#include <iomanip>
#include <sstream>
#include <vector>
#include <string>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
#include <functional>
#include <iterator>
#include <limits>
#include <numeric>
#include <utility>
#include <cmath>
#include <cassert>
#include <cstdio>

using namespace std; using namespace placeholders;

using LL = long long;
using ULL = unsigned long long;
using VI = vector< int >;
using VVI = vector< vector< int > >;
using VS = vector< string >;
using SS = stringstream;
using PII = pair< int, int >;
using VPII = vector< pair< int, int > >;
template < typename T = int > using VT = vector< T >;
template < typename T = int > using VVT = vector< vector< T > >;
template < typename T = int > using LIM = numeric_limits< T >;

template < typename T > inline istream& operator>>( istream &s, vector< T > &v ){ for ( T &t : v ) { s >> t; } return s; }
template < typename T > inline ostream& operator<<( ostream &s, const vector< T > &v ){ for ( int i = 0; i < int( v.size() ); ++i ){ s << ( " " + !i ) << v[i]; } return s; }
template < typename T > inline T fromString( const string &s ) { T res; istringstream iss( s ); iss >> res; return res; };
template < typename T > inline string toString( const T &a ) { ostringstream oss; oss << a; return oss.str(); };

#define REP2( i, n ) REP3( i, 0, n )
#define REP3( i, m, n ) for ( int i = ( int )( m ); i < ( int )( n ); ++i )
#define GET_REP( a, b, c, F, ... ) F
#define REP( ... ) GET_REP( __VA_ARGS__, REP3, REP2 )( __VA_ARGS__ )
#define FOR( e, c ) for ( auto &e : c )
#define ALL( c ) ( c ).begin(), ( c ).end()
#define AALL( a, t ) ( t* )a, ( t* )a + sizeof( a ) / sizeof( t )
#define DRANGE( c, p ) ( c ).begin(), ( c ).begin() + p, ( c ).end()

#define SZ( v ) ( (int)( v ).size() )
#define PB push_back
#define EM emplace
#define EB emplace_back
#define BI back_inserter

#define EXIST( c, e ) ( ( c ).find( e ) != ( c ).end() )

#define MP make_pair
#define fst first
#define snd second

#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

#include <random>

mt19937 rng;
uniform_int_distribution< int > rng_idx( 1, 19 );
uniform_real_distribution< double > rng_p( 0, 1 );

constexpr int SIM = 1000000;

int N;
double Pa, Pb;

inline int select( const double p, VI &as )
{
	if ( SZ( as ) == 1 )
	{
		return as[0];
	}
	else if ( rng_p( rng ) <= p )
	{
		const int res = as[0];
		as.erase( as.begin() );
		return res;
	}
	else
	{
		rng_idx.param( uniform_int_distribution< int >::param_type( 1, SZ( as ) - 1 ) );
		const int idx = rng_idx( rng );
		const int res = as[ idx ];
		as.erase( as.begin() + idx );
		return res;
	}
}

inline bool sim( VI as, VI bs )
{
	int pt1 = 0, pt2 = 0;

	REP( i, N )
	{
		const int a = select( Pa, as );
		const int b = select( Pb, bs );

		if ( a < b )
		{
			pt2 += a + b;
		}
		if ( a > b )
		{
			pt1 += a + b;
		}
	}

	return pt1 > pt2;
}

int main()
{
	cin.tie( 0 );
	ios::sync_with_stdio( false );

	cin >> N >> Pa >> Pb;

	VI as( N ), bs( N );
	cin >> as >> bs;

	sort( ALL( as ) );
	sort( ALL( bs ) );

	int win = 0;
	REP( i, SIM )
	{
		win += sim( as, bs );
	}

	cout << setprecision( 5 ) << fixed << 1. * win / SIM << endl;

	return 0;
}