//	Ex443.cc

//	Sec. 4.4 of lecture
//	FOR-loop
//				Example : sum of even natural numbers

#include <iostream.h>

main()
{
 int   i,isum,n;			// loop index, sum, last index
 
 cout << endl << "  Sum of even numbers " << endl;
 cout << endl << "  n = ";
 cin  >> n;				// initialize last index

 isum = 0;				// initialize sum (integer !)
 
 for ( i = 2; i <= n; i+=2)
   {
     isum = isum +i;
   }
 
 cout << endl << "  Sum of first " << n/2 << " even numbers = " << isum << endl; 
 cout << endl;
}