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

//first one :A-Z:0-25
//the other :A-Z:1-26
int main(){
  long int n;
  int m;
  bool flag = true;
  string ans = "";
  vector<int> q;
  
  cin >> n;
  
  do{
    if(flag){
      m=n%26;
      n=n/26;
      flag = !flag;
    }
    else{
      m=n%27;
      n=n/27;
    }
    ans = char('A'+m)+ans;
    
  }while(n>26);
  ans = char('A'+n-1)+ans;
  cout << ans << endl;
}