#include<iostream>

using namespace std;

int  main()
{
int a,b,c,d,e;
  
 while(1)
 {cin>>a>>b>>c>>d;
  if ((b-a)==(c-b))
  e=d+(b-a);
   
  else if ((a*c)==(b*b))
  e=d*d/c;
  
 cout<<a<<b<<c<<d<<e<<"\n"; 
}

   
return 0;
}

 出來是......

RE (SIGKILL)
執行時期錯誤

產生立即終止訊號!!  Killed 

Your loop doesn't end.

Also, print a blank between numbers.

Read the problem carefully.