#include <bits/stdc++.h>
using namespace std;
const long long MAX = 1e6;
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long k;
  cin >> k;
  if (k == 0) {
    cout << "ab";
    return 0;
  }
  for (char c = 'a'; c <= 'z' && k; ++c) {
    long long d = sqrt(1 + 8 * k);
    long long n = (d - 1) / 2;
    for (long long i = 0; i < n + 1; ++i) cout << c;
    k -= n * (n + 1) / 2;
  }
}
