import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

# cnt=0
# x = 1
# def ask(q):
#     global cnt
#     cnt+=1
#     print("?", q)
#     return abs(x-q) <= abs(x-p)

def ask(q):
    print("?", q, flush=True)
    return II()

# l, r = 0, 1000
l, r = 0, 10**6+1
p = (l*2+r)//3
print("?", p, flush=True)
big = 1
while r-l > 2:
    if big:
        q = (l+r*2)//3
        near = ask(q)
        if near:
            m = (p+q+1)//2
            l = m-1
            p = q
        else:
            m = (p+q)//2
            r = m+1
            big = 0
    else:
        q = (l*2+r)//3
        near = ask(q)
        if near:
            m = (p+q)//2
            r = m+1
            p = q
        else:
            m = (p+q+1)//2
            l = m-1
            big = 1
    # print(l, r, p, q, big)

print("!", l+1, flush=True)
# print(cnt)