#include <bits/stdc++.h>
using namespace std;
const long long inf = (1ll << 62) - 1;
const long long MOD = 1e9 + 7;
const int MAX = 2 * 1e9 + 10;
const int N = 2e5 + 5;
using namespace std;
int bPow(int a, int b) {
  int res = 1;
  while (b) {
    if (b & 1ll) {
      res = 1ll * res * a % MOD;
    }
    b >>= 1;
    a = 1ll * a * a % MOD;
  }
  return res;
}
int gcd(int a, int b) {
  if (a < b) {
    swap(a, b);
  }
  if (b == 0) return a;
  return gcd(b, a % b);
}
vector<int> mpf(N, 0);
void sieve() {
  for (int i = 2; i < N; ++i) {
    if (!mpf[i])
      for (int j = 2 * i; j < N; j += i) {
        mpf[j] = i;
      }
  }
}
void solve() {
  long long k;
  cin >> k;
  string ans;
  for (char c = 'a'; c <= 'z'; c++) {
    long long cnt = 1;
    while (k >= cnt * (cnt + 1) / 2) cnt++;
    cnt--;
    long long n = cnt * (cnt + 1) / 2;
    k -= n;
    ans += string(cnt + 1, c);
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int tc = 1;
  while (tc--) {
    solve();
  }
  return 0;
}
