#include <bits/stdc++.h>
using namespace std;
int arr[1000000], n;
long long fc(long long num) {
  if (num == 1) return 1;
  long long nm = (sqrt(8 * num + 1) - 1) / 2;
  return nm;
}
int main(int argc, char const *argv[]) {
  std::vector<long long> v;
  cin >> n;
  if (n == 0) {
    cout << 'a';
    return 0;
  }
  while (n) {
    long long cnt = fc(n);
    v.push_back(cnt + 1);
    n = n - (cnt * (cnt + 1)) / 2;
  }
  for (int i = 0; i < v.size(); ++i) {
    long long nm = v[i];
    for (int j = 0; j < nm; ++j) {
      char x = 'a' + i;
      cout << x;
    }
  }
  return 0;
}
