#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1e9 + 7;
const long long int maxn = 2e5 + 10;
long long int maxnn = 1e18;
double pie = 3.1415926535;
int main() {
  long long int k, i, n, x;
  bool flag = true;
  char j = 'a';
  cin >> k;
  while (flag == true) {
    n = (-1 + sqrtl(1 + 8 * k)) / 2;
    for (i = 0; i <= n; i++) cout << j;
    j++;
    x = (n * (n + 1)) / 2;
    k = k - x;
    if (k <= 0) flag = false;
  }
}
