#include <bits/stdc++.h>
using namespace std;
mt19937 rnd(228);
int main() {
  int n = 1000000;
  vector<long long> dp(n + 1);
  dp[1] = 0;
  for (int i = 2; i <= n; i++) {
    if (i % 2 == 0) {
      dp[i] = dp[i / 2] * 2 + (i / 2) * (long long)(i / 2);
    } else {
      dp[i] = dp[i / 2] + dp[i / 2 + 1] + (i / 2) * (long long)(i / 2 + 1);
    }
  }
  int k;
  cin >> k;
  int x = k;
  string ans = "";
  int ch = 0;
  while (k) {
    if (dp[n] <= k) {
      for (int i = 0; i < n; i++) ans += (ch + 'a');
      ch++;
      k -= dp[n];
    } else {
      n--;
    }
  }
  if (x == 0) {
    ans = "a";
  }
  cout << ans << '\n';
}
