#include <bits/stdc++.h>
int gcd(int a, int b) { return a == 0 ? b : gcd(b % a, a); }
void clean_stdin(void) {
  int c;
  do {
    c = getchar();
  } while (c != '\n' && c != EOF);
}
void debug() {
  clean_stdin();
  printf("press any key to continue\n");
  scanf("%*c");
}
using namespace std;
long long k;
vector<long long> ans;
string s;
long long fun(long long k) {
  long long l = 1, r = 1e4, mid, flag = 1;
  while (l < r) {
    mid = l + (r - l) / 2;
    if (flag = 1 - flag) mid++;
    if (mid * (mid - 1) / 2 <= k) {
      l = mid;
    } else {
      r = mid - 1;
    }
  }
  return l;
}
int main() {
  cin >> k;
  if (k == 0) {
    cout << "a" << endl;
    return 0;
  }
  while (k > 0) {
    long long x = fun(k);
    ans.push_back(x);
    k = k - x * (x - 1) / 2;
  }
  s = "";
  for (int i = 0; i < ans.size(); i++) {
    while (ans[i] > 0) {
      s.push_back('a' + i);
      ans[i]--;
    }
  }
  cout << s << endl;
  return 0;
}
