#include <iostream>
using namespace std;

int main(){
   long long n;
   string s = "";
   cin >> n;
   if(n == 0){
      cout << 'A' << endl;
      return 0;
   }
   while(n != 0){
      n--;
      s += char('A' + n % 26);
      n /= 26;
   }
   for(int i = s.size() - 1;i != -1;i--) cout << s[i];
   cout << endl;
}