#include <bits/stdc++.h>
using namespace std;
int n;
void solve() {
  if (n == 0) {
    printf("ldz\n");
    return;
  }
  for (int times = 0; n; times++) {
    int k = 0;
    for (int i = 1; i * (i - 1) / 2 <= n; k = (i++))
      ;
    n -= k * (k - 1) / 2;
    for (int i = 1; i <= k; i++) printf("%c", 'a' + times);
  }
}
int main() {
  scanf("%d", &n);
  solve();
  return 0;
}
