#include <bits/stdc++.h>
using namespace std;
const int maxn = 0;
const int mo = 0;
int k, cnt;
int main() {
  cin >> k;
  for (int i = 0; i < 26; i++) {
    cnt = 0;
    while ((cnt + 1) * cnt / 2 <= k) cnt++;
    k -= cnt * (cnt - 1) / 2;
    for (int j = 0; j < cnt; j++) printf("%c", 'a' + i);
  }
  return 0;
}
