#include <bits/stdc++.h>
using namespace std;
int k;
const int max_n = 100000;
const int last_i = 490;
int help[last_i + 1];
void answer() {
  vector<int> ans;
  int index = last_i;
  while (k) {
    if (help[index] <= k) {
      k -= help[index];
      ans.push_back(index);
    } else {
      index--;
    }
  }
  assert(ans.size() <= 27);
  for (int i = 0; i < ans.size(); ++i) {
    char ch = 'a' + i;
    for (int j = 0; j < ans[i]; ++j) {
      cout << ch;
    }
  }
  cout << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  int ans = 1;
  int add = 2;
  help[0] = 0;
  help[1] = 0;
  for (int i = 2; i <= last_i; ++i) {
    help[i] = ans;
    ans += add;
    add++;
  }
  cin >> k;
  if (k == 0) {
    cout << 'a' << endl;
  } else {
    answer();
  }
  return 0;
}
