#include <iostream>
using namespace std;

int main()
{
  long long n;
  char s[11];
  cin >> n;
  s[11]='\0';
  s[10]='A'+n%26;
  n/=26;
  int i=0;
  for(;n>0;n/=26)
  {
    ++i;
    s[10-i]='A'+n%26;
  }
  cout << (s+10-i) << endl;
  return 0;
}