#include "bits/stdc++.h"

using namespace std;

static void solve()
{
  long long num;
  cin >> num;
  string ans;
  while (true) {
    ans = static_cast<char>(num % 26 + 'A') + ans;
    if (num < 26) break;
    num /= 26;
    num--;
  }
  cout << ans << "\n";
}

int main()
{
  ios::sync_with_stdio(false);
  cin.tie();
  solve();
}