#include<iostream>
#include<string>
#include<vector>
using namespace std;
int main(){
  long long n;
  cin >> n;
  vector<char> str;
  while(n){
    str.push_back(n%26+'A');
    n/=26;
  }
  while(str.size()){
    cout<<str.back();
    str.pop_back();
  }
  cout<<endl;
  return 0;
}