#include <bits/stdc++.h>
using namespace std;
long long n, l, r, k, c, i;
string s;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n;
  if (n == 0) {
    cout << "a"
         << "\n";
    return 0;
  }
  while (n > 0) {
    l = 1;
    r = 100000;
    k++;
    while (l < r) {
      c = (l + r) / 2;
      if (c * (c - 1) / 2 > n)
        r = c;
      else
        l = c + 1;
    }
    if (l * (l - 1) / 2 > n) l--;
    n -= (l * (l - 1) / 2);
    for (i = 1; i <= l; i++) s += char(96 + k);
  }
  cout << s << "\n";
  return 0;
}
