#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using ii = pair<ll, ll>;
using vi = vector<ll>;
using vii = vector<ii>;
using vb = vector<bool>;
using vvi = vector<vi>;
using vvii = vector<vii>;
constexpr int INF = 1e9 + 1;
constexpr ll LLINF = 1e18 + 1;
int main() {
  ll k;
  cin >> k;
  if (k == 0) cout << 'a';
  char n = 'a';
  while (k > 0) {
    ll i = 1;
    while (i * (i - 1) / 2 <= k) ++i;
    --i;
    k -= i * (i - 1) / 2;
    while (i--) cout << n;
    ++n;
  }
  cout << endl;
  return 0;
}
