#include <bits/stdc++.h>
const int N = 1e5 + 9;
using namespace std;
long long sum[N];
int vis[N];
int main() {
  sum[1] = 0;
  for (int i = 2; i <= 1e5 + 1; ++i) sum[i] = sum[i - 1] + i - 1;
  int k;
  cin >> k;
  if (k == 0) {
    putchar('a');
    return 0;
  }
  for (int i = 1e5; i >= 2; --i)
    while (k >= sum[i]) {
      k = k - sum[i];
      vis[i]++;
    }
  int tot = 0;
  for (int i = 1e5; i >= 0; --i)
    for (int j = 1; j <= vis[i]; ++j) {
      for (int k = 1; k <= i; ++k) putchar(tot + 'a');
      tot++;
    }
}
