#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main(){
    long long n;cin>>n;
    if(n==0){
      cout << "A" << endl;
      return 0;
    }
    string s;
    while(n != 0){
        s.push_back('A'+n%26);
        n/=26;
    }
    reverse(s.begin(),s.end());
    if(s.size()!=1)s[0]--;
    cout << s << endl;
}