#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-6;
const int MAXN = 1005;
const int MAXM = 300005;
const long long LINF = 0x3f3f3f3f3f3f3f3f;
const int INF = 0x3f3f3f3f;
const double FINF = 1000000000000000.0;
const long long MOD = 1000000007;
const double PI = acos(-1);
vector<int> v;
void init() {
  v.push_back(0);
  for (int i = 1; i <= 1000; ++i) v.push_back(i * (i + 1) / 2);
}
int main() {
  int k, tot;
  init();
  tot = 0;
  scanf("%d", &k);
  if (k == 0) {
    printf("a\n");
    return 0;
  }
  while (k != 0) {
    int pos = upper_bound(v.begin(), v.end(), k) - v.begin();
    k -= v[pos - 1];
    for (int i = 0; i < pos; ++i) {
      printf("%c", tot + 'a');
    }
    tot++;
  }
}
