Problem2429--Infinite Inversions

2429: Infinite Inversions

Time Limit: 2 Sec  Memory Limit: 256 MB
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Description

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).

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