Min Sum Path in Matrix

Given a 2D integer array A of size M x N, you need to find a path from top left to bottom right which minimizes the sum of all numbers along its path.

NOTE: You can only move either down or right at any point in time.

First and only argument is an 2D integer array A of size M x N.

Return a single integer denoting the minimum sum of a path from cell (1, 1) to cell (M, N).

Input 1:

 A = [  [1, 3, 2]
        [4, 3, 1]
        [5, 6, 1]
     ]

Output 1:

 8

Explanation 1:

 The path is 1 -> 3 -> 2 -> 1 -> 1
 So ( 1 + 3 + 2 + 1 + 1) = 8