#include <bits/stdc++.h>
using namespace std;
int k;
int a[1000];
const int n = 1000;
int main() {
  cin >> k;
  if (k == 0) {
    cout << "a" << endl;
  } else {
    for (int i = 0; i < n; ++i) {
      a[i] = i * (i - 1) / 2;
    }
    char c = 'a';
    while (k > 0) {
      int d = upper_bound(a, a + n, k) - a;
      d--;
      k -= a[d];
      for (int i = 0; i < d; ++i) {
        cout << c;
      }
      c++;
    }
    cout << endl;
  }
  return 0;
}
