Let M1,M2, ..., MN be the medians and let MM be the median of medians.
So (N-1)/2 medians are less than MM and (N-1)/2 medians are greater than MM. Since each of these medians has (N-1)/2 elements less and greater than themselves within each computer, there are (N-1)/2*(N-1)/2 (this is I mentioned *around* N^2/4) elements less than MM and same number greater than MM. What exactly are these numbers is obtained by partitioning. Overall time complexity is O(N) with all computers running parallel since each step takes O(N) time.
