#include <bits/stdc++.h>
#define REP(i, a, n) for(ll i = ((ll) a); i < ((ll) n); i++)
#define MOD 1000000007LL
using namespace std;
typedef long long ll;

ll N;

string dfs(ll n, char &chr) {
  if(n == 1) return "";

  string ret;
  if(n % 2 == 0) {
    ret = dfs(n / 2, chr);
    ret = chr + ret;
  } else {
    ret = dfs(n - 1, chr);
    if(chr == 'z') chr = 'a';
    else chr = chr + 1;
    ret = chr + ret;
  }
  return ret;
}

int main(void) {
  ll N;
  cin >> N;

  if(N == 1) {
    cout << "a" << endl;
    return 0;
  }

  char chr = 'a';
  string ans = dfs(N, chr);
  cout << ans;
  reverse(ans.begin(), ans.end());
  cout << ans << endl;
}