#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  scanf("%d", &k);
  ;
  for (int x = 0; x < 26; x++) {
    int cnt = 1;
    while ((cnt * (cnt + 1) / 2) <= k) cnt++;
    k -= cnt * (cnt - 1) / 2;
    for (int y = 0; y < cnt; y++) printf("%c", ('a' + x));
    if (k == 0) break;
  }
}
