#include <bits/stdc++.h>
int arr[1005];
int n;
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int sum = 0;
  for (int i = 0; i < 505; i++) {
    sum += i;
    arr[i + 1] = sum;
  }
  if (n == 0) {
    printf("a\n");
    return 0;
  }
  for (int i = 0; i < 26; i++) {
    if (n == 0) {
      return 0;
    }
    int howmany = lower_bound(arr, arr + 500, n) - arr;
    if (arr[howmany] == n) {
      for (int j = 0; j < howmany; j++) {
        printf("%c", 'a' + i);
      }
      printf("\n");
      return 0;
    }
    if (arr[howmany] > n) {
      n -= arr[howmany - 1];
      for (int j = 0; j < howmany - 1; j++) {
        printf("%c", 'a' + i);
      }
      continue;
    }
  }
  return 0;
}
