#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, i = 0, j = 0, k = 0, l = 0, m = 0, a = 0, b = 0, sum = 0, x = 0,
               y = 0, z = 0, c, p = 0;
  cin >> k;
  string s, t;
  for (i = 0; i < 26; i++) {
    x = 1;
    while (((x + 1) * x) / 2 <= k) {
      x++;
    }
    k -= ((x - 1) * x) / 2;
    for (j = 0; j < x; j++) {
      s.push_back('a' + i);
    }
  }
  cout << s;
  return 0;
}
