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

namespace
{
int A[ 1010 ];
}

int main()
{
int i;
int N;
int x;

	cin >> N;
	for( i = 0; i < N; i++ ) cin >> A[ i ];

	sort( A, A + N );

	if( N % 2 == 1 )
		cout << A[ N / 2 ] << endl;
	else
	{
		i = N / 2;
		x = A[ i - 1 ] + A[ i ];
		if( x < 0 )
		{
			cout << "-";
			x *= - 1;
		}

		if( x % 2 == 1 )
			cout << x / 2 << ".5" << endl;
		else
			cout << x / 2 << endl;
	}

	return 0;
}