#include <bits/stdc++.h>
using namespace std;

int f(int n) {
	return n * (n + 1) / 2;
}

int main() {
	int N; cin >> N;
	char a = 'a';
	while (N > 0) {
		int n;
		for (n = 1; f(n + 1) <= N; n++);
		N -= f(n);
		while (n--) cout << a;
		a++;
	}
	cout << endl;
}