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

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