#include <bits/stdc++.h>
using namespace std;
template <class TH>
void _dbg(const char *sdbg, TH h) {
  cerr << sdbg << "=" << h << "\n";
}
template <class TH, class... TA>
void _dbg(const char *sdbg, TH h, TA... a) {
  while (*sdbg != ',') cerr << *sdbg++;
  cerr << "=" << h << ",";
  _dbg(sdbg + 1, a...);
}
long long test;
long long n;
void solve() {
  cin >> n;
  string s;
  long long cur = 0;
  for (auto it = 'a'; it <= 'z'; it++) {
    while ((cur * (cur + 1)) / 2 <= n) {
      s += it;
      cur++;
    }
    cur--;
    n -= (cur * (cur + 1)) / 2;
    if (n == 0) {
      break;
    }
    cur = 0;
  }
  cout << s;
  return;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout.precision(10);
  cout << fixed;
  test = 1;
  while (test--) {
    solve();
  }
  return 0;
}
