CSU-ACM2017暑期训练12-KMP F - 前缀后缀

F - 前缀后缀

Asterix, Obelix and their temporary buddies Suffix and Prefix has finally found the Harmony temple. However, its doors were firmly locked and even Obelix had no luck opening them.

A little later they found a string s, carved on a rock below the temple's gates. Asterix supposed that that's the password that opens the temple and read the string aloud. However, nothing happened. Then Asterix supposed that a password is some substring t of the string s.

Prefix supposed that the substring t is the beginning of the string s; Suffix supposed that the substring t should be the end of the string s; and Obelix supposed that t should be located somewhere inside the string s, that is, t is neither its beginning, nor its end.

Asterix chose the substring t so as to please all his companions. Besides, from all acceptable variants Asterix chose the longest one (as Asterix loves long strings). When Asterix read the substring t aloud, the temple doors opened.

You know the string s. Find the substring t or determine that such substring does not exist and all that's been written above is just a nice legend.

You are given the string s whose length can vary from 1 to 106 (inclusive), consisting of small Latin letters.

Print the string t. If a suitable t string does not exist, then print "Just a legend" without the quotes.

Input

fixprefixsuffix

Output

fix

Input

abcdabc

Output

Just a legend

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
const int maxn = 1e6 + 10;

char s[maxn], sample[maxn];
int Next[maxn], anotherNext[maxn];
bool vis[maxn];

void getNext(int nex[], char str[]){
int len = strlen(str);
nex[0] = nex[1] = 0;
int j;
for(int i = 1; i < len; i++){
j = nex[i];
while(j && s[i] != s[j])
j = nex[j];
if(s[i] == s[j])
nex[i + 1] = j + 1;
else
nex[i + 1] = 0;
}
}

bool check(){
int len = strlen(s);
for(int i = 0; i < len; i++)
vis[Next[i]] = true;
int k = len;
while(Next[k] != 0){ // 非常巧妙之处。
if(vis[Next[k]]){
for(int j = 0; j < Next[k]; j++)
putchar(s[j]);
putchar('\n');
return true;
}
k = Next[k];
}
return false;
}

int main(){
#ifdef TEST
freopen("test.txt", "r", stdin);
#endif // TEST

while(scanf("%s", s) != EOF){
memset(Next, 0, sizeof(Next));
memset(vis, false, sizeof(vis));
int len = strlen(s);
getNext(Next, s);
if(!check())
printf("Just a legend\n");
}

return 0;
}