s = input().lower()
a = []
for j in s:
a.append(j)
a.sort()
print(a.count(a[-1]) * a[-1])#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main()
{
string s;
cin >> s;
char c = *max_element(s.begin(), s.end());
for (int i = 0; i < s.size(); i++)
{
if (s[i] == c)
cout << s[i];
}
}
318. Maximum Product of Word Lengths | 448. Find All Numbers Disappeared in an Array |
1155. Number of Dice Rolls With Target Sum | 415. Add Strings |
22. Generate Parentheses | 13. Roman to Integer |
2. Add Two Numbers | 515. Find Largest Value in Each Tree Row |
345. Reverse Vowels of a String | 628. Maximum Product of Three Numbers |
1526A - Mean Inequality | 1526B - I Hate 1111 |
1881. Maximum Value after Insertion | 237. Delete Node in a Linked List |
27. Remove Element | 39. Combination Sum |
378. Kth Smallest Element in a Sorted Matrix | 162. Find Peak Element |
1529A - Eshag Loves Big Arrays | 19. Remove Nth Node From End of List |
925. Long Pressed Name | 1051. Height Checker |
695. Max Area of Island | 402. Remove K Digits |
97. Interleaving String | 543. Diameter of Binary Tree |
124. Binary Tree Maximum Path Sum | 1465. Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts |
501A - Contest | 160A- Twins |