import sys
import math

low = 1
high = 10**9 + 1
ans = 1

while low <= high:
    center = math.floor((low + high)/2)
    print('?', center)
    sys.stdout.flush()
    r = input()
    if r == '1':
        ans = center
        low = center + 1
    else:
        high = center - 1

print('!', ans)
sys.stdout.flush()