#include <bits/stdc++.h>
using namespace std;
void Main() {
  u_int64_t N;
  cin >> N;
  N--;
  vector<char> ans;
  u_int64_t alphabet_size = 'z' - 'a' + 1;
  u_int64_t base = alphabet_size;
  while (N / base > 0) {
    ans.push_back('a' + N % base);
    N /= base;
  }
  ans.push_back('a' + N % base);
  for (u_int64_t i = 1; i < ans.size(); i++) {
    ans[i]--;
  }
  if (ans.size() == 1) {
    ans[0]--;
  }
  reverse(ans.begin(), ans.end());
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i];
  }
  cout << endl;
}
int main() {
  std::cout << std::fixed << std::setprecision(15);
  Main();
  return 0;
}
