#include <bits/stdc++.h>
using namespace std;
char maxOccuringChar(string text)
{
int maxfreq = 0;
char maxchar;
map<char,int> freq;
for (char c : text)
{
freq[c]++;
if (freq[c] > maxfreq)
{
maxfreq = freq[c];
maxchar = c;
}
}
return maxchar;
}
int main() {
string text;
cin >> text;
cout << maxOccuringChar(text);
}
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