#include <bits/stdc++.h>
using namespace std;
int dx[4] = {0, 0, -1, 1};
int dy[4] = {1, -1, 0, 0};
int main() {
  int k;
  cin >> k;
  int fre[26] = {};
  int i = 0;
  while (i < 26 && k >= 0) {
    int x = 1;
    while (x * (x + 1) / 2 <= k) x++;
    fre[i] = x;
    k -= x * (x - 1) / 2;
    i++;
  }
  for (int i = 0; i < 26; i += 1)
    for (int j = 0; j < fre[i]; j += 1) cout << (char)('a' + i);
  cout << '\n';
}
