#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main(){
    long long n;cin>>n;n++;
    string s;
    //ひとけた目
    while(n != 0){
      s.push_back(((n%26)==0?'Z':'A'+(n%26)-1));
      n = (n-1)/26;
    }
    reverse(s.begin(),s.end());
    cout << s << endl;
}