哈希

#define ll unsigned long long
ll gt(int x,int y) {return (hash[y]-hash[x-1]*mi[y-x+1]);}
for (ll i=1;i<=N;i++) mi[i]=mi[i-1]*S;
for (ll i=1;i<=l1;i++) hash[i]=(hash[i-1]*S+s1[i]-'A'+1);