#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>
#include <iterator>

using namespace std;

const int LIMIT = 5e4;

int main() {
	int n;

	cin >> n;
	vector<long long> counts(LIMIT, 0);

	for (long long i = 0; i < counts.size(); i++) {
		counts[i] = i * (i + 1) / 2;
	}

	string ans;
	int c_idx = 0;

	while (n > 0) {
		auto it = upper_bound(counts.begin(), counts.end(), n);
		it--;

		ans.append(distance(counts.begin(), it), 'a' + c_idx);
		n -= *it;
		c_idx = (c_idx + 1) % 26;
	}

	cout << ans << endl;
	return 0;
}