#include <iostream>
#include <vector>
using namespace std;

int main(){
  long int n;
  int m;
  vector<int> q;
  cin >> n;
  string ans = "";
  
  if(n<=25)
    ans = char('A'+n);
  else{
    do{
      m=n%26;
      n=n/26;
      if(n==0){
	ans = char('A'+m-1)+ans;
      }
      else
	ans = char('A'+m)+ans;
    }while(n!=0);

  }
  cout << ans << endl;
}