十年OI一场空，______________。
还有就是 Cs,t=∑s≠v,t≠vCs,v×Cv,t(diss,t=diss,v+disv,t)C_{s, t}^{}=\sum_{s \ne v, t \ne v}C_{s, v} \times C_{v, t} (dis_{s, t} = dis_{s, v} + dis_{v, t})Cs,t=∑s=v,t=vCs,v×Cv,t(diss,t=diss,v+disv,t)
