#include <bits/stdc++.h>
using namespace std;
vector<char> a;
string s = "0abcdefghijklmnopqrstuvwxyz";
int main() {
  long long n;
  cin >> n;
  while (n > 1) {
    if (n % 26 == 0)
      a.push_back('z');
    else
      a.push_back(s[n % 26]);
    n /= 26;
  }
  reverse(a.begin(), a.end());
  for (int i = 0; i < a.size(); i++) cout << a[i];
  return 0;
}
