#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 10;
int k;
long long tn[MAXN];
int main() {
  for (long long i = 1; i <= 1000; ++i) {
    tn[i] = i * (i - 1) / 2;
  }
  while (cin >> k) {
    if (k == 0) {
      cout << "a" << endl;
      continue;
    }
    char ta = 'a';
    while (k) {
      int ti = upper_bound(tn + 1, tn + 1000, k) - tn;
      --ti;
      int tm = tn[ti];
      k -= tm;
      for (int i = 0; i < ti; ++i) {
        printf("%c", ta);
      }
      ++ta;
    }
    cout << endl;
  }
  return 0;
}
