#include <iostream>

using namespace std;

int main()
{
   int a,b,c;
   1<=a,b,c<=10;
   cin>>a;
  cin>>b;
  cin>>c;

   if(b-a=c-b)
   {
       cout<<"the arrangment is beautiful"<<endl;
   }
   else
   {
       cout<<"the arrangement is not beautiful"<<endl;
   }


}
