#include <bits/stdc++.h>
using namespace std;
const long long maxn = 1e5 + 100, mod = 1e9 + 7, INF = 1ll << 62;
int a[26];
int main() {
  long long k, t, x = 0;
  cin >> k;
  if (k == 0) {
    cout << "a";
    return 0;
  }
  t = 1000;
  while (k > 0) {
    if (t * (t - 1) / 2 <= k) {
      k -= t * (t - 1) / 2;
      a[x] = t;
      x++;
    } else {
      t--;
    }
  }
  for (int i = 0; i < 26; i++) {
    for (int j = 0; j < a[i]; j++) {
      cout << char(int('a') + i);
    }
  }
}
