Two arrays of integers `a` and `b` are given, both sorted in non-decreasing order. Determine how many pairs `(i, j)` can be formed such that `a[i] == b[j]`, following this rule: traverse both arrays simultaneously with two indices, and each element may be used at most once in a pair. In other words, once `a[i]` is paired with `b[j]`, both indices advance and cannot be reused. This is exactly the pair-counting variant of the merge algorithm. Input: The program reads from standard input: - a natural number `n`, followed by `n` integers (array `a`); - a natural number `m`, followed by `m` integers (array `b`). - `1 <= n, m <= 1000` - `-1000000 <= values <= 1000000` - the arrays are sorted in non-decreasing order and may contain duplicates Output: The program prints to standard output a single non-negative integer: the total number of equal pairs formed, followed by a newline. Example: Input: 5 1 2 3 4 5 3 2 4 6 Output: 2