def query(x):
    print(int(x))
    r = int(input())
    assert r != -1
    return r

if query(1e9):
    print(int(1e9))
    exit()

ok = 0
ng = 1e9 // 2
while ng - ok > 1:
    md = (ok + ng) // 2
    
    if query(2 * md) == 1:
        ok = md
    else:
        ng = md

print(2 * ok)