#include <bits/stdc++.h>
using namespace std;
const long long MAX = 1e3 + 10;
const long long INF = 1e8;
const long long MOD = 1e9 + 7;
int main() {
  int n, i, j, k, l, p, q, x, y;
  vector<int> a, c;
  for (i = 1; i <= 500; i++) {
    a.push_back((i * (i + 1)) / 2);
    c.push_back(i + 1);
  }
  cin >> n;
  if (n == 0) {
    cout << 'a';
    return 0;
  }
  vector<char> b;
  i = 0;
  while (n) {
    l = lower_bound(a.begin(), a.end(), n) - a.begin();
    k = a[l];
    if (n != k) {
      p = c[l - 1];
      k = a[l - 1];
      for (j = 0; j < p; j++) b.push_back(char(97 + i));
      n = n - k;
    } else {
      p = c[l];
      for (j = 0; j < p; j++) b.push_back(char(97 + i));
      n = n - k;
    }
    i++;
  }
  for (auto t : b) cout << t;
}
