#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
const int INF = 1 << 29;
const double EPS = 1e-9;
const ll MOD = 1000000007;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, -1, 0, 1};
ll K;
string result;
ll calc(ll K) {
  ll left, right;
  left = 0;
  right = 1 << 25;
  while (right - left > 1) {
    ll med = (right + left) / 2;
    if (med * (med + 1) / 2 <= K) {
      left = med;
    } else {
      right = med;
    }
  }
  return left;
}
int main() {
  cin >> K;
  if (K == 0) {
    cout << 'a' << endl;
    return 0;
  }
  char c = 'a';
  while (K > 0) {
    ll res = calc(K);
    for (int i = 0; i <= res; i++) {
      result += c;
    }
    K -= res * (res + 1) / 2;
    c++;
  }
  cout << result << endl;
  return 0;
}
