#include <bits/stdc++.h>
using namespace std;
const double PI = acos(0) * 2;
const double EPS = 1e-8;
const long long MOD = 1e9 + 7;
const int MAXN = 1e5 + 5;
const int oo = 1e9;
const double foo = 1e30;
template <class T>
int getbit(T s, int i) {
  return (s >> i) & 1;
}
template <class T>
T onbit(T s, int i) {
  return s | (T(1) << i);
}
template <class T>
T offbit(T s, int i) {
  return s & (~(T(1) << i));
}
template <class T>
int cntbit(T s) {
  return __builtin_popcounll(s);
}
template <class T>
T sqr(T x) {
  return x * x;
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
long long n;
int main() {
  cin >> n;
  if (n == 0) {
    cout << "a";
    return 0;
  }
  int now = 0;
  while (n) {
    long long l = 0, r = n + 5, find = -1;
    while (l <= r) {
      long long mid = (l + r) >> 1;
      if (mid * (mid - 1) / 2ll <= n) {
        find = mid;
        l = mid + 1;
      } else
        r = mid - 1;
    }
    long long tmp = find * (find - 1) / 2ll;
    n -= tmp;
    char c = (now + 'a');
    for (int i = 0; i < find; i++) cout << c;
    now++;
  }
}
