Finding repeated numbers in two arrays

Given two sorted integer arrays (array size may differ).

Find the number of values that appear in both arrays.

For example, given:

A: 1, 3, 5, 8, 10. 14, 16, 25, 28, 47
B: 2, 4, 7, 8, 11, 12, 14, 17, 47, 56, 64

The result should be 3, since value 8, 14, 47 appear in both array.

Hint: A simple approach would take O(m+n) however it can be done in O(nlogm) (a better bound if n is very small as compared to m)