#include <bits/stdc++.h>
using namespace std;
int n, p;
int main() {
  scanf("%d", &n);
  if (!n) {
    putchar('a');
    return 0;
  }
  while (n) {
    int x = 2;
    for (; (long long)x * (long long)(x + 1) / 2LL <= n; x++)
      ;
    n -= (long long)x * (x - 1) / 2LL;
    for (; x; x--) putchar('a' + p);
    p++;
  }
  return 0;
}
