Young Photographer

题意翻译

题目描述：在一个坐标轴上给出一些区间，和一个点，问这些区间的公共部分距离这个点的最近距离，如果不存在，那么输出-1 输入：第一行两个整数，一个正整数N表示区间个数，第二个整数代表开始时的位置x0 之后N行每行两个整数表示一个区间 输出：如题目描述 1<=n<=100 0<=x0<=1000 0<=ai,bi<=1000 ai!=bi Translated by 稀神探女

题目描述

Among other things, Bob is keen on photography. Especially he likes to take pictures of sportsmen. That was the reason why he placed himself in position $ x_{0} $ of a long straight racetrack and got ready to take pictures. But the problem was that not all the runners passed him. The total amount of sportsmen, training at that racetrack, equals $ n $ . And each of them regularly runs distances within a particular segment of the racetrack, which is the same for each sportsman. For example, the first sportsman runs from position $ a_{1} $ to position $ b_{1} $ , the second — from $ a_{2} $ to $ b_{2} $ What is the minimum distance that Bob should move to have a chance to take pictures of each sportsman? Bob can take a picture of a sportsman, if he stands within the segment that this sportsman covers on the racetrack.

输入输出格式

输入格式

The first line of the input file contains integers $ n $ and $ x_{0} $ ( $ 1<=n<=100 $ ; $ 0<=x_{0}<=1000 $ ). The following $ n $ lines contain pairs of integers $ a_{i},b_{i} $ ( $ 0<=a_{i},b_{i}<=1000 $ ; $ a_{i}≠b_{i} $ ).

输出格式

Output the required minimum distance in the same units as the positions on the racetrack. If there is no such a position, output -1.

输入输出样例

输入样例 #1

3 3
0 7
14 2
4 6

输出样例 #1

1