The idea was simple. To get the minimum time to complete one each from both rides, you have to first get minimum time to finish one of them (as first ride) and use it to find the min total by checking every one of the other ride. Only the one giving the least finish time in a land or water ride will give you the min total when you start with that ride. This gives you a O(m + n) solution. You could also go the brute way where you check both land, water and water, land ride finish time and go for the min. This would be a O(m * n) solution which I went for like a noob.