The end is always closer than you think.
身体单薄无力,就不要去背负重物,说话没有分量,就不要去规劝别人;没有钱就不要到人群中去,遭遇困难之际千万别去寻求亲戚的帮助。
A problem is in P if it can be solved quickly by a computer, and in NP if a solution can be verified quickly.