Integer Intervals
Description:
An integer interval [a,b], a < b, is a set of all consecutive integers beginning with a and ending with b.
Write a program that: finds the minimal number of elements in a set containing at least two different integers from each interval.
Input:
The first line of the input contains the number of intervals n, 1 <= n <= 10000. Each of the following n lines contains two integers a, b separated by a single space, 0 <= a < b <= 10000. They are the beginning and the end of an interval.
Output:
Output the minimal number of elements in a set containing at least two different integers from each interval.
Sample Input:
4 3 6 2 4 0 2 4 7
Sample Output:
4
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