#include <bits/stdc++.h>
using namespace std;
const int INF = 1e4 + 5;
int k;
int F(int x) { return x * (x + 1) / 2; }
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> k;
  for (int it = 0; it < 26; it++) {
    int l = 0, r = INF, pos = 0;
    while (l <= r) {
      int mid = (l + r) >> 1;
      if (F(mid) <= k) {
        pos = mid;
        l = mid + 1;
      } else {
        r = mid - 1;
      }
    }
    k -= F(pos);
    char alf = char(int('a') + it);
    for (int i = 0; i <= pos; i++) cout << alf;
    if (k == 0) break;
  }
  cout << '\n';
  return 0;
}
