5236: Infinite Inversions
内存限制：256 MB
时间限制：2 S
题面：传统
评测方式：文本比较
上传者：
提交：1
通过：1
题目描述
E. Infinite Inversions
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
There is an infinite sequence consisting of all positive integers in the increasing order: p={1,2,3,...}. We performed n swap operations with this sequence. A swap(a,b) is an operation of swapping the elements of the sequence on positions a and b. Your task is to find the number of inversions in the resulting sequence, i.e. the number of such index pairs (i,j), that i<j and pi>pj.
Input
The first line contains a single integer n (1≤n≤105)− the number of swap operations applied to the sequence. Each of the next n lines contains two integers ai and bi (1≤ai,bi≤109, ai≠bi)− the arguments of the swap operation.
Output
Print a single integer − the number of inversions in the resulting sequence.
Examples
Input
2 4 2 1 4
Output
4
Input
3 1 6 3 4 2 5
Output
15
Note
In the first sample the sequence is being modified as follows: 
. It has 4 inversions formed by index pairs (1,4), (2,3), (2,4) and (3,4). 输入样例 复制
输出样例 复制