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松塔先生决定在他的电脑上下载原神来玩，但是他的队友灵妹妹觉着玩游戏实在是太浪费时间了，于是灵妹妹给松塔先生的原神下载界面上了锁，并丢给松塔先生一串字符。
现在有三种子串：
1.子串是该字符串的前缀
2.子串是该字符串的后缀
3.子串既不是该字符串的前缀也不是该字符串的后缀
密码就是满足这三种条件的最长子串。
即密码既是字符串的前缀，又是字符串的后缀，且在字符串中以非前后缀的形式出现过。
但是松塔先生太懒了，宁可睡觉也不解密码，请你帮助他。
特别的，由于灵妹妹特别的狡猾，密码可能根本就不在这串字符串里，如果是这样，输出"Play what play,Roll to study"
Input
多行由小写英文字母组成的字符串，长度n(1<=n<=1e6)
Output
多行字符串，原神下载页面的密码或者"Play what play,Roll to study"
末尾有换行
Sample Input
abcdefabcghaabc
abc
Sample Output
abc
Play what play,Roll to study
#include<iostream> using namespace std; int main() {
ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr); string
a,b,c,d; while(cin>>a) { b=a; int k=0,num=0,kb=-1; reverse(b.begin(),b.end());
string A,B; A.empty(); B.empty(); for(int i=0;i<(int)a.length()-1;i++) {
A+=a[i]; B+=b[i]; for(int j=0;j<(int)A.length();j++) {
if(a[j]==b[A.length()-j-1]) k=0; else { k=1; break; } } if(k==0) { c=A; int
pos=a.find(c,1); if((pos+c.length()-1)<(a.length()-1)) { int len=c.length();
if(len>kb) { kb=len; d=c; num=1; } } else continue; } } if(num==0) cout<<"Play
what play,Roll to study"<<endl; else cout<<d<<endl; } return 0; }
