#include <bits/stdc++.h>
using namespace std;
long long int dp[1000005];
int a[30];
int main() {
  int t, k, i, j, n, m, x, y, q, c, d;
  dp[0] = 0;
  dp[1] = 0;
  for (i = 2; i < 1000005; i++)
    dp[i] = dp[i / 2] + dp[i - i / 2] + i / 2 * 1LL * (i - i / 2);
  cin >> k;
  if (k == 0) {
    cout << "a";
    return 0;
  }
  for (i = 0; i < 26 && k; i++) {
    int low = 0, high = 1000000, mid;
    while (low < high) {
      mid = low + (high - low + 1) / 2;
      if (dp[mid] <= k)
        low = mid;
      else
        high = mid - 1;
    }
    a[i] = low;
    k -= dp[low];
  }
  for (i = 0; i < 26; i++) {
    char ch = 'a' + i;
    if (a[i])
      while (a[i]--) cout << ch;
  }
  return 0;
}
