def query(x):
    print(x)
    res = int(input())
    return res


lo = 1
hi = 10 ** 9
ans = 0
for _ in range(30):
    m = (lo + hi) // 2
    res = query(m)
    if res == 1:
        ans = max(ans, m)
        lo = m
    else:
        hi = m

print(ans)