#include<iostream.h>

void main() 
{
   int a ;
   int b ;
   int c ;
   int d ;

   cout << "Enter a: " ;
   cin >> a ;
   cout << "Enter b: " ;
   cin >> b ;
   cout << "Enter c: " ;
   cin >> c ;
   cout << "Enter d: " ;
   cin >> d ;

   cout << (a+c)*d - (a*b) ;
   cout << endl ;

}