#include <bits/stdc++.h>
using namespace std;
const int N = 100000 + 10;
const int M = 1000000007;
const double PI = atan(1) * 4;
const int oo = 1000000000;
int k;
string ans;
int main() {
  cin >> k;
  int tot = 0;
  if (!k) return cout << "a", 0;
  for (int l = 0; l < 26 && tot < k; ++l) {
    int fr = 1;
    while (tot + fr * (fr - 1) / 2 <= k) ++fr;
    --fr;
    tot += fr * (fr - 1) / 2;
    for (int i = 0; i < fr; ++i) ans += l + 'a';
  }
  assert(tot == k);
  printf("%s\n", ans.c_str());
}
