#include <algorithm>
#include <iomanip>
#include <iostream>
#include <vector>

using namespace std;

int main() {
    int N;
    cin >> N;
    vector< int > A( N );
    for ( int i = 0; i < N; i++ ) cin >> A[ i ];
    vector< int > B( N );
    for ( int i = 0; i < N; i++ ) cin >> B[ i ];

    vector< int > ord1( N ), ord2( N );
    for ( int i = 0; i < N; i++ ) ord1[ i ] = ord2[ i ] = i;

    double win = 0.0;
    double game = 0.0;
    do {
        do {
            game += 1.0;
            int a = 0, b = 0;
            for ( int i = 0; i < N; i++ ) {
                if ( A[ ord1[ i ] ] > B[ ord2[ i ] ] ) a++;
                else if ( A[ ord1[ i ] ] < B[ ord2[ i ] ] ) b++;
            }
            if ( a > b ) win += 1.0;
        } while ( next_permutation( ord2.begin(), ord2.end() ) );
        for ( int i = 0; i < N; i++ ) ord2[ i ] = i;
    } while ( next_permutation( ord1.begin(), ord1.end() ) );

    cout << setprecision( 10 ) << win / game << endl;
}