#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  n++;
  Int l=0,b=1;
  while(b<=n){
    n-=b;
    l++;
    b*=26;
  }
  //cout<<n<<" "<<l<<endl;
  string s(l,'#');
  for(Int i=0;i<l;i++)
    s[i]=char('A'+n%26),n/=26;
  reverse(s.begin(),s.end());
  cout<<s<<endl;
  return 0;
}