Sum of positive elements in odd rows

Given a two-dimensional array with dimensions n x m, your task is to calculate the sum of all positive elements located in the odd-numbered rows of this array.

Input Data

The first line of input consists of two integers, n and m (1 ⩽ n, m ⩽ 100), representing the number of rows and columns, respectively. Following this, there are n lines, each containing m integers, which represent the elements of the array. Note that row numbering starts at 1.

Output Data

Output a single integer, which is the sum of the positive elements in the odd-numbered rows.

Examples