#include<iostream>
#include<string>
#include<vector>
using namespace std;
pair<int, string> fun(const string &str)
{
	vector<string> substrs;
	int len = str.length();
	string substring;
	int maxcount(0);
	//后缀数组
	for (int i = 0; i < len; ++i)
	{
		substrs.push_back(str.substr(i));
		// cout << substrs[i] << endl;
	}
	for (int i = 0; i < len; ++i)
	{
		for (int j = 1; j <= len; j++) {
			int count = 1;
			int sublen = j;
			for (int k = i + 1; k < len; k++) {
				
				if (substrs[k].length() < sublen) {
					break;
				}
				string str1 = substrs[i].substr(0, sublen);
				string str2 = substrs[k].substr(0, sublen);
				if (str1.compare(str2)==0)
				{
					++count;
				}
			}
			if (count > maxcount||(count == maxcount && sublen > substring.length()))
			{
				maxcount = count;
				substring = substrs[i].substr(0, sublen);
			}
		}
	}
	return make_pair(maxcount, substring);
}

int main()
{
	string str;
    int len;
    cin >> len;
    cin >> str;
	auto res = fun(str);
	cout << res.first << endl;
	// cout << "the matched substring is:" << res.second << endl;
	return 0;
}