import sys

Max=10**9+7
Min=0
while Max - Min>4:
    Mid = (Max + Min)//2
    print("? "+str(Mid))
    #exit()
    sys.stdout.flush()
    res = int(input())
    #print(res)
    if res == 1:
        Min=Mid
    else:
        Max=Mid
    #print(Max,Min)
    
for i in range(Min,Max+10):
    print("? "+str(i))
    sys.stdout.flush()
    res = int(input())
    if res == 1:
        print("! "+str(i))
        exit()
        sys.stdout.flush()