#include <bits/stdc++.h>
using namespace std;
const int M = 400010, mod = 1000000007;
int C[M];
int rev[M];
vector<int> p;
int main() {
  int i, j, k, n;
  scanf("%d", &n);
  if (n == 0) {
    printf("a\n");
    return 0;
  }
  for (i = 1; (i * (i - 1)) / 2 < M; i++)
    C[i] = (i * (i - 1)) / 2, rev[C[i]] = i;
  i--;
  while (i > 0 && n > 0) {
    if (C[i] <= n) {
      n -= C[i];
      p.push_back(i);
    } else
      i--;
  }
  int c = 0;
  for (int a : p) {
    for (i = 0; i < a; i++) printf("%c", c + 'a');
    c++;
  }
  printf("\n");
  return 0;
}
