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];
}
}
1711A - Perfect Permutation | 1701B - Permutation |
1692A - Marathon | 1066A - Vova and Train |
169B - Replacing Digits | 171D - Broken checker |
380C - Sereja and Brackets | 1281B - Azamon Web Services |
1702A - Round Down the Price | 1681C - Double Sort |
12A - Super Agent | 1709A - Three Doors |
1680C - Binary String | 1684B - Z mod X = C |
1003A - Polycarp's Pockets | 1691B - Shoe Shuffling |
1706A - Another String Minimization Problem | 1695B - Circle Game |
1702B - Polycarp Writes a String from Memory | 1701A - Grass Field |
489C - Given Length and Sum of Digits | 886B - Vlad and Cafes |
915A - Garden | 356A - Knight Tournament |
1330A - Dreamoon and Ranking Collection | 1692B - All Distinct |
1156C - Match Points | 1675A - Food for Animals |
1328C - Ternary XOR | 1689A - Lex String |