#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T>
using vec = vector<T>;
template <class T>
using vvec = vector<vec<T>>;
template <class T>
bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int K;
  cin >> K;
  int M = 1000;
  vec<int> A(M + 1);
  int num = 0;
  if (K == 0) {
    cout << "a\n";
    return 0;
  }
  for (int i = 1; i <= M; i++) {
    A[i] = i * (i - 1) / 2;
    if (A[i] <= K) num = i;
  }
  char now = 'a';
  string ans = "";
  while (K) {
    K -= A[num];
    for (int i = 0; i < num; i++) ans += now;
    while (A[num] > K) num--;
    now++;
  }
  cout << ans << "\n";
}
