Pappu is an aspiring politician and he decides to follow PM's foot steps. So he began working at a tea stall.

At the end of the day there are total N tea cups, some of them are half filled and rest are empty. Pappu has to bring back all of them to the dishwasher. In each trip he brings back some of the cups. He can merge the contents of two half filled cups, and thus would be left with one full cup and an empty cup. He has to follow certain constraints, given below.

He cannot put a (half/full) filled cup on any other cup. However, he can stack any number of empty cups together.
He cannot put any cup on a (half/full) filled cup.

Pappu is entertaining but not that smart. You have to help him to find out minimum number of trips required to bring back all the cups.

INPUT :

The first line of the input contains a single integer N.

The Second line of the input contains N space separated integers. Each integer is either 0 or 1 .

Integer 0 represents an empty cup and 1 represents an half-filled cup.

OUTPUT:

Print out a single integer which is equal to the minimum number of trips required for pappu to bring all the N tea cups to the dishwasher.

CONSTRAINTS:

1 ≤ N ≤ 100

Each integer is either 0 or 1