def query(y):
    print('?', y, flush=True)
    v = int(input())
    return v

ok = 0
ng = 10**9+1
while ok+1 < ng:
    mid = (ok+ng)//2
    v = query(mid)
    if v == 1:
        ok = mid
    else:
        ng = mid
print('!', ok)