#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, K;
  char c, *p, bf[100008];
  while (scanf("%d", &K) == 1) {
    p = bf;
    for (c = 'a'; K != 0; c++) {
      for (n = 1; n * (n + 1) / 2 <= K; n++)
        ;
      n--;
      K -= n * (n + 1) / 2;
      n++;
      while (n--) *p++ = c;
    }
    *p++ = c;
    *p = '\0';
    puts(bf);
  }
  return 0;
}
