n = int(eval(input()))



for i in range(n, 0, -1):

  if str(i ** 0.5)[-1] == "0":

    print(i)

    exit()
import math

n = int(eval(input()))

print((math.floor(n**0.5)**2))
n = int(eval(input()))
for i in range(n, 0, -1):
    if str(i**0.5)[-1] == "0":
        print(i)
        exit()

import math

n = int(eval(input()))
print((math.floor(n**0.5) ** 2))

+import math + -for i in range(n, 0, -1): -    if str(i**0.5)[-1] == "0": -        print(i) -        exit() +print((math.floor(n**0.5) ** 2))