#include <iostream>
#include <algorithm>
#include <iterator>
#include <fstream>
#include <limits>
#include <cassert>
#include <functional>
#include <set>
#include <vector>
#include <iomanip>
#include <numeric>

using namespace std;

int main() {
	assert( numeric_limits<long>::max() > 1000000000 );

	typedef multiset< long, greater<long> > score_set;
	score_set scores;
	typedef vector< long > rank_set;
	rank_set ranks;

	ifstream in( "s5.in" );
//	  istream &in = cin;

	long cases_left = 0;
	in >> cases_left;
	ranks.reserve( cases_left );
	long current_score;	   
	while ( cases_left-- && ( in >> current_score ) ) {

		score_set::iterator pos = scores.lower_bound( current_score );
		long this_rank = 1 + distance( scores.begin(), pos );
		scores.insert( pos, current_score );
		ranks.push_back( this_rank );	 
//	  	  cerr << this_rank << " of " << scores.size() << endl;
	
	}

	double mean_rank = accumulate( ranks.begin(), ranks.end(), 0.0 )
					   / ranks.size();
	cout << fixed << setprecision(2) << mean_rank << endl;	  	  
	
	return 0;
}