15
MIRZOYANOVECLOX
 23
AABBBAAACCCCCAAADDDDDDD
 2
QA
 11
GGRRAATTZZZ
 6
AZAZAZ
 10
SQSQSQSQTG
 3
KEK
 100
URXCAIZFIBNJTPCZHBQIBCILLPXZCFGMKKZMNPLCYGAVJVIBMCZEBSJWPSCPQDYCTTKPOKIJRSKIZPDGCHVOUTMPNECYORSFZFNC
 3
LOL
 2
WW
 8
PUTINVOR
 26
QWERTYUIOPASDFGHJKLZXCVBNM
 5
AZAZA
 9
EGORLETOV
 7
KADUROV
 9
MIKEPIDOR
 9
AAAAAAAAA
 100
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
 5
FUFEL
 50
NYQAHBYYOXLTRYQDMVENEMAQNBAKGLGQOLXNAIFNQTOCLNNQIA

MI
 DD
 QA
 ZZ
 AZ
 SQ
 KE
 IB
 LO
 WW
 PU
 QW
 AZ
 EG
 KA
 MI
 AA
 AA
 FU
 YQ

#include <bits/stdc++.h>
using namespace std;
int Substr(string str, string sub) {
  int nRet = 0, nStart = 0;
  while (-1 != (nStart = str.find(sub, nStart))) {
    nStart += sub.length();
    ++nRet;
  }
  return nRet;
}
int main() {
  string s;
  while (cin >> s) {
    getchar();
    int maxn = 0;
    string ans;
    for (int i = 0; i < s.size(); i++) {
      for (int j = i + 1; j < s.size(); j++) {
        string str = s.substr(i, j - i + 1);
        int num = Substr(s, str);
        if (maxn < num) {
          maxn = num;
          ans = str;
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}
