#include <iostream>
using namespace std;

int main()
{
  long long n;
  string s;
  cin >> n;
  s+=(char)('A'+n%26);
  n/=26;
  for(;n>0;n/=26)
  {
    s+=(char)('A'+n%26);
  }
  cout << s << endl;
  return 0;
}