Complement Intervals

Given a list of time intervals during a day, your task is to determine the free time slots that are not covered by any of the intervals. The day is represented as the interval \([0,1440)\) in minutes. Note that the provided intervals may overlap or be adjacent.

If there is any gap between the intervals, output each free interval on a separate line as two integers representing the start and end of the free slot. If the entire day is covered by the intervals, output No free interval.

inputFormat

The first line of input is an integer n (0 ≤ n ≤ 1000), the number of intervals. The next n lines each contain two space-separated integers a and b (0 ≤ a < b ≤ 1440) representing an interval [a, b].

outputFormat

If there is any free interval, output each interval on a new line as two space-separated integers (start and end). If no free interval exists, output No free interval instead.

3
0 100
150 300
1200 1440

100 150
300 1200