Takahashi is streaming from one hour to another. You need to find out how many of his listeners can watch the whole stream without missing any part of it.
Input: 19, 22, [[17, 23], [20, 23], [19, 22], [0, 23], [12, 20]]
Output: 3
Input: 12, 13, [[0, 1], [0, 1], [0, 1]]
Output: 0