var n=Int(readLine()!)!
var arr=readLine()!.characters.split{$0==" "}.map{Int(String($0))!}

var i = 0
var d : Double = 0

arr = arr.sort() 
//print( arr )

d = ( ( Double(arr[0]) + Double(arr[1]) ) / 2 )
//print( d )
for i in 2..<n {
  d = ( ( d + Double(arr[i]) ) / 2)
}
       
print( d )