#include <bits/stdc++.h>
using namespace std;
long long arr[6666666];
map<long long, long long> vis1;
map<long long, long long> vis2;
signed main() {
  long long cnt = 1;
  for (;; cnt++) {
    arr[cnt] = (cnt * (cnt - 1) / 2);
    vis1[arr[cnt]] = 1;
    vis2[arr[cnt]] = cnt;
    if (arr[cnt] > 100009) {
      break;
    }
  }
  long long K;
  cin >> K;
  if (!K) {
    cout << "ac";
    return 0;
  }
  if (vis1[K]) {
    for (long long i = 0; i < vis2[K]; i++) cout << "a";
    return 0;
  }
  long long tot = 0;
  while (K) {
    long long pos = 1;
    while (K >= arr[pos]) pos++;
    pos--;
    K -= arr[pos];
    for (long long i = 0; i < pos; i++) printf("%c", tot + 'a');
    tot++;
  }
  return 0;
}
