#include <bits/stdc++.h>
using namespace std;
long long int gcd(long long int a, long long int b) {
  return b == 0 ? a : gcd(b, a % b);
}
long long power(long long a, long long b) {
  long long ret = 1;
  while (b) {
    if (b % 2 == 1) ret = (ret * a) % 1000000007;
    a = (a * a) % 1000000007;
    b /= 2;
  }
  return ret;
}
int main() {
  int k;
  cin >> k;
  if (k == 0) {
    cout << "a";
    return 0;
  }
  string ans = "";
  int st = 0;
  while (k) {
    int num = 1;
    while (num * (num + 1) / 2 <= k) num++;
    num--;
    k -= num * (num + 1) / 2;
    for (int i = 0; i <= num; i++) ans.push_back(st + 'a');
    st++;
  }
  cout << ans;
  return 0;
}
