Group Them All!!!

“United we stand, divided we fall” – says the professor. There are N students in the college and there is large disunity among students.The size of any group is the number of students in it. The professor wants to group them into a large single group(of size N). He knows that each student has its own skill level given by the array skill[ ] and that every student is a group of its own(of size 1).