#include<bits/stdc++.h>
using namespace std;
void Out(long long X)
{
  if(X==0)
    return ;
X--;
  long long Rem=X%26ll;
  Out(X/26ll);
  cout<<(char)(Rem+'a');
}
int main()
{
  long long X;
  cin>>X;
  Out(X);
  return 0;
}
