流水

All with Pairs 题意 记f(s,t)f(s,t)f(s,t)为最大的iii使得s1...i=t∣t∣−i+1...∣t∣s_{1...i} =t_{\left|t\right|-i+1...\left|t\right|}s1...i​=t∣t∣−i+1...∣t∣​ 给nnn个串s1,s2,...,sns_1,s_2,...,s_ns1​,s2​,...,sn​，求∑i=1n∑j=1nf(si,sj)2\displaystyle\sum_{i = 1} ^ n\displaystyle\sum