#include<bits/stdc++.h>

using namespace std;

int main( void )
{
    int N;
    cin >> N;
    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];
    }

    vector<int> perm_A( N ), perm_B( N );
    iota( perm_A.begin(), perm_A.end(), 0 );
    int win_count = 0, game_count = 0;
    do
    {
        iota( perm_B.begin(), perm_B.end(), 0 );
        do
        {
            int tmp = 0;
            for( int i = 0; i < N; i++ )
            {
                if( A[perm_A[i]] > B[perm_B[i]] ) tmp++;
            }
            if( tmp > N / 2 ) win_count++;
            game_count++;
        } while ( next_permutation( perm_B.begin(), perm_B.end() ) );
    } while ( next_permutation( perm_A.begin(), perm_A.end() ));
    
    cout << ( double )win_count / ( double )game_count << endl;

    return 0;
}