output_description: Print the largest square number not exceeding N.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: import math
  
  
  def A():
      a, b = [int(x) for x in input().split()]
      print(math.ceil((a + b) / 2))
  
  
  def B():
      a = "".join(sorted(list(input()), key=lambda x: ord(x)))
      b = "".join(sorted(list(input()), key=lambda x: -ord(x)))
      if a < b:
          print("Yes")
      else:
          print("No")
  
  
  def C():
      N = input()
      A = [x for x in input().split()]
      counter = {}
  
      for a in A:
          if a in counter:
              counter[a] += 1
          else:
              counter[a] = 1
      remove_count = 0
      for key in counter:
          if counter[key] - int(key) >= 0:
              remove_count += counter[key] - int(key)
          else:
              remove_count += counter[key]
      print(remove_count)
  
  
  def E():
      s1 = input()
      s2 = input()
      if s1 == s2[::-1]:
          print("YES")
      else:
          print("NO")
  
  
  def F():
      a = int(input())
      sqrt = math.floor(math.sqrt(a))
      print(sqrt * sqrt)
  
  
  F()
  
problem_description: Statement
  
  Find the largest square number not exceeding N. Here, a _square number_ is an
  integer that can be represented as the square of an integer.
samples: [{"input": "10", "output": "9\n    \n\n10 is not square, but 9 = 3 \u00d7 3 is. Thus, we print 9.\n\n* * *"}, {"input": "81", "output": "81\n    \n\n* * *"}, {"input": "271828182", "output": "271821169"}]