#include <bits/stdc++.h>
using namespace std;
template <typename S, typename T>
ostream& operator<<(ostream& out, pair<S, T> const& p) {
  out << '(' << p.first << ", " << p.second << ')';
  return out;
}
template <typename T>
ostream& operator<<(ostream& out, vector<T> const& v) {
  long long l = v.size();
  for (long long i = 0; i < l - 1; i++) out << v[i] << ' ';
  if (l > 0) out << v[l - 1];
  return out;
}
template <typename T>
void trace(const char* name, T&& arg1) {
  cout << name << " : " << arg1 << "\n";
}
template <typename T, typename... Args>
void trace(const char* names, T&& arg1, Args&&... args) {
  const char* comma = strchr(names + 1, ',');
  cout.write(names, comma - names) << " : " << arg1 << " | ";
  trace(comma + 1, args...);
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long k;
  cin >> k;
  if (k == 0) {
    cout << "a"
         << "\n";
    return 0;
  }
  vector<long long> ans;
  while (k > 0) {
    long long low = 0, high = 10000, curr = 0;
    while (low <= high) {
      long long mid = low + (high - low) / 2;
      if ((mid * (mid + 1)) / 2 <= k) {
        curr = mid;
        low = mid + 1;
      } else
        high = mid - 1;
    }
    k -= ((curr * (curr + 1)) / 2);
    ans.push_back(curr);
  }
  string s;
  char c = 'a';
  for (long long i = 0; i < ans.size(); i++) {
    for (long long j = 0; j < ans[i] + 1; j++) {
      s += c;
    }
    c++;
  }
  cout << s << "\n";
  return 0;
}
