#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 5;
int n;
string res;
void solve(int k, char c) {
  if (!k) {
    res += c;
    return;
  }
  int mx = -1;
  for (int i = 1; ((1LL * i * (i + 1)) / 2) <= k; ++i) {
    mx = i;
  }
  assert(mx != -1);
  for (int i = 1; i <= mx + 1; ++i) {
    res += c;
  }
  k -= ((1LL * mx * (mx + 1)) / 2);
  c += 1;
  solve(k, c);
}
int main() {
  int k;
  cin >> k;
  if (!k) {
    cout << "a" << endl;
    return 0;
  }
  solve(k, 'a');
  cout << res << endl;
  return 0;
}
