def check(n):
    print(n)
    a = int(input())
    if(a == 1 or a == -1):exit()
    return False

ok,ng = 1,10**9
while(ng - ok > 1):
    mid = (ok+ng)//2
    if(check(mid)):
        ok = mid
    else:
        ng = mid
print(ok)