#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
const double eps = 0.0000000001;
const int INF = 1e9;
const int N = 10000 + 100;
int n, k;
int main() {
  cin >> n;
  for (int i = 1; i <= 26; i++) {
    k = 1;
    while (k * (k + 1) / 2 <= n) k++;
    n -= k * (k - 1) / 2;
    for (int j = 1; j <= k; j++) printf("%c", 'a' + i - 1);
  }
  return 0;
}
