#include <bits/stdc++.h>
using namespace std;

int check( const vector< int > &a, const vector< int > &b ){
  int win = 0, lose = 0;
  for( int i = 0; i < a.size(); ++i )
    win += a[ i ] > b[ i ],
    lose += a[ i ] < b[ i ];
  return win > lose;
}

signed 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 ];
  sort( A.begin(), A.end() );
  sort( B.begin(), B.end() );
  int rnd_cnt = 0;
  int win_cnt = 0;
  do{
    do{
      ++rnd_cnt;
      win_cnt += check( A, B );
    } while( next_permutation( B.begin(), B.end() ) );
  } while( next_permutation( A.begin(), A.end() ) );
  cout << fixed << setprecision( 6 ) << 1.0 * win_cnt / rnd_cnt << endl;
  return 0;
}