#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const int INF = 1 << 30;
int MAXN = 1e7 + 2;
const double eps = 1e-13;
vector<int> s;
int main() {
  for (int i = (2); i < (5000); ++i) {
    s.push_back((i * (i - 1)) / 2);
  }
  int(n);
  scanf("%d", &n);
  printf("a");
  int x = 1;
  while (n > 0) {
    int p = upper_bound((s).begin(), (s).end(), n) - s.begin();
    n -= *(upper_bound((s).begin(), (s).end(), n) - 1);
    for (int i = 0; i < (p + 1); ++i) printf("%c", 'a' + x);
    x++;
  }
  puts("");
}
