#ifndef MYDEBUG
#include <bits/stdc++.h>
#define err(...)
#define errs(...)
#endif

using namespace std;
void Calc();
#define ALL(a) begin(a),end(a)
#define RALL(a) rbegin(a),rend(a)
typedef long long ll;
typedef unsigned long long ull;
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  cin.exceptions(istream::failbit | istream::badbit);
  Calc();
  cout.flush();
  return 0;
}

struct Scanner {
  template<class A = string>static A Next() { A a; cin >> a; return a; }
  static string Line() { string s; getline(cin, s); return s; }
  template<class A = int> static vector<A> Array(int n) {
    vector<A> a(n); for (A& i : a) i = Next<A>(); return a;
  }
  template<class A = int> static vector<A> Array(int n, A add) {
    vector<A> a(n); for (A& i : a) i = Next<A>() + add; return a;
  }
  static int Int() { return Next<int>(); }
  template<class A> A operator-(const A &a) { return Next<A>() - a; }
  template<class A> Scanner& operator>>(A &a) { a = Next<A>(); return *this; }
  template<class A> operator A() { return Next<A>(); }
  operator bool() { return !!cin; }
};
Scanner in;

/*---------------------------------------------------------------------*/

void Calc() {
  ll n = in;
  vector<int> a;
  for (; 0 <= n; n = n / 26 - 1) {
    if (n == 0) {
      a.push_back(0);
      break;
    }
    ll k = n;
    int c = n % 26;
    a.push_back(c);
  }
  for_each(a.rbegin(), a.rend(), [](int i) {
    cout << static_cast<char>(i + 'A');
  });
  cout << endl;
}