import math
import sys
def binary_search_guessing_game():
upperBoundary = int(input("input"))
sys.stdout.flush()
lowerBoundary = 1
finalGuess = None
for _ in range(50):
guess = math.floor((upperBoundary + lowerBoundary) / 2)
print(f"? {guess}")
sys.stdout.flush()
response = int(input())
if response == 0:
finalGuess = guess
break
elif response == 1:
upperBoundary = guess - 1
elif response == -1:
lowerBoundary = guess + 1
if finalGuess is not None:
print(f"= {finalGuess}")
sys.stdout.flush()
binary_search_guessing_game()
