#include <bits/stdc++.h>
using namespace std;
long long int check(long long int n) {
  long long int l = 1, r = 100001;
  while (l <= r) {
    long long int mid = (l + r) / 2;
    long long int p = ((mid + 1) * mid) / 2;
    long long int p1 = ((mid + 2) * (mid + 1)) / 2;
    long long int p2 = ((mid) * (mid - 1)) / 2;
    if (p2 <= n && p > n) return mid - 1;
    if (p <= n && p1 > n) {
      return mid;
    }
    if (p < n)
      l = mid + 1;
    else
      r = mid - 1;
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    long long int i, j, n, k, l, p = 1, m, r, q = 97;
    cin >> n;
    string s = "", s1 = "a";
    if (n == 0) {
      cout << s1 << endl;
      continue;
    }
    while (n > 0) {
      k = check(n);
      s1[0] = (char)(q);
      q++;
      for (i = 0; i <= k; i++) {
        s = s + s1;
      }
      n = n - ((k * (k + 1)) / 2);
    }
    cout << s << endl;
  }
  return 0;
}
