from sys import exit
def meguru_bisect(ng,ok):
    while (abs(ok - ng) > 1):
        mid = (ok + ng + 1) // 2 
        if is_ok(mid):
            ok = mid
        else:
            ng = mid
    return ok


def is_ok(arg):
    print(arg)
    x = int(input())
    if x == 0:
        return True
    else:
        exit()
    pass

meguru_bisect(1,10**9)