#include <bits/stdc++.h>
using namespace std;
long long k;
long long verify(string &a, long long k) {
  map<char, int> all;
  long long re = 0;
  for (char i : a) {
    re += all[i];
    all[i]++;
  }
  return re == k;
}
string rsp(int &a, char cykaa) {
  int left = 'z' - cykaa + 1;
  if (a <= left) {
    string re = "";
    while (a > 0) {
      a--;
      re += cykaa;
      cykaa++;
    }
    return re + re;
  }
  long long rsp = 1;
  long long kek = 0;
  while (kek < a) {
    rsp++;
    kek = rsp * (rsp - 1) / 2;
  }
  if (kek > a) rsp--;
  kek = rsp * (rsp - 1) / 2;
  a -= kek;
  string ree(rsp, cykaa);
  return ree;
}
string rspe(int k) {
  if (k == 0) return "a";
  char cykaa = 'a';
  string re = "";
  while (k > 0) {
    re += rsp(k, cykaa);
    cykaa++;
  }
  return re;
}
int main() {
  cin >> k;
  cout << rspe(k);
}
