#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, sum = 0;
  scanf("%d", &k);
  if (k == 0) {
    cout << "a" << endl;
    return 0;
  }
  string res = "";
  for (char i = 'a'; i <= 'z'; ++i) {
    if (sum == k) break;
    for (int j = 0; j + sum <= k; ++j) {
      sum += j;
      res += i;
    }
  }
  printf("%s", res.c_str());
  return 0;
}
