#include <bits/stdc++.h>
using namespace std;
long long solve(long long k) {
  long long lo = 1, hi = k;
  while (lo <= hi) {
    long long md = (lo + hi) / 2;
    if (md * (md + 1) <= k)
      lo = md + 1;
    else
      hi = md - 1;
  }
  return lo - 1;
}
int main() {
  long long k;
  cin >> k;
  if (k == 0) {
    cout << 'a';
    return 0;
  }
  char ch = 'a';
  while (k > 0) {
    long long ret = solve(2 * k);
    k = k - (ret * (ret + 1)) / 2;
    for (long long i = 1; i <= ret + 1; i++) cout << ch;
    ++ch;
  }
}
