#include <bits/stdc++.h>
using namespace std;
const int N = (int)1e7;
const int MOD = (int)1e9 + 7;
const int inf = (int)5e8;
const long long infll = (long long)1e17;
void solve() {
  int k;
  scanf("%d", &k);
  if (k == 0) {
    cout << "a\n";
    return;
  }
  vector<string> ans;
  for (int i = 0; i < 26 && k > 0; ++i) {
    int l = 0;
    int r = k + 10;
    while (r - l > 1) {
      int mid = (r + l) / 2;
      long long cnt = mid * 1ll * (mid - 1) / 2;
      if (cnt <= k) {
        l = mid;
      } else {
        r = mid;
      }
    }
    k -= l * 1ll * (l - 1) / 2;
    ans.push_back(string(l, 'a' + i));
  }
  for (auto& i : ans) {
    cout << i;
  }
  cout << "\n";
}
int main() {
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
