def main():
    t = 10**9//2
    a = t
    m = 0
    M = 10**9
    while True:
        t //= 2
        print("? {0:}".format(a))
        t += t == 0
        if "1" == input():
            m = a
            a += t
        else:
            M = a
            a -= t
        if m + 1 == M:
            break
    print("! {0:}".format(m))

if __name__ == "__main__":
    import sys
    import os
    if len(sys.argv) > 1:
        if sys.argv[1] == "-d":
            #filename = "input1.txt"
            #fd = os.open(filename, os.O_RDONLY)
            #os.dup2(fd, sys.stdin.fileno())
            main()
    else:
        main()