#include <bits/stdc++.h>
using namespace std;
int maxi;
string s, t;
map<string, int> a;
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> s;
	for(int i = 0; i < s.size(); i++){
		t = s[i];
		a[t]++;
		for(int j = i + 1; j < s.size(); j++){
			t = s[i];
			t += s[j];
			a[t]++;
		}
	}
	map<string, int>::iterator it;
	for (it = a.begin(); it != a.end(); it++)
	{
		maxi = max(maxi, it->second);
	}
	cout << maxi;
}

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