#include <iostream>
using namespace std;
int n;
int next[114514];
string cut ( string str, int start, int end )
{
	string tmp;
	for ( int i = start; i <= end; i++ )
	{
		tmp += str[i];
	}
	return tmp;
}
int main()
{
	cin >> n;
	string to;
	for ( int i = 1; i <= n; i++ )
	{
		string back;
		back = to;
		for ( int k = 1; k <= i; k++ )
		{
			to += char ( k + 'a' - 1 );
			if ( cut ( to, 1, k ) == cut ( to, i - k + 1, i ) && k >= n )
			{
				cout << to;
				return 0;
			}
		}
		to = back;
	}
	return 0;
}