#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, n, tmp;
  string s;
  char c;
  scanf("%d", &n);
  c = 'b';
  s = "a";
  for (i = 1000; i >= 2; i--) {
    tmp = i * (i - 1) / 2;
    while (n >= tmp) {
      n -= tmp;
      for (j = 0; j < i; j++) s.push_back(c);
      c++;
    }
  }
  printf("%s\n", s.c_str());
  return 0;
}
