#842 · #1942 · The Number of the Smallest Unoccupied Chair(最小未被占据椅子的编号)

There are infinitely many chairs numbered 0, 1, 2, .... Friends arrive at times[i][0] and leave at times[i][1], and each sits on the smallest-numbered free chair. Return the chair that targetFriend sits on. All arrival times are distinct. Constraints: 1 <= times.length <= 10^4, 0 <= times[i][0] < times[i][1] <= 10^5, 0 <= targetFriend < times.length.