codeforces 540 E. Infinite Inversions (离散化 + 树状数组)

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.

Sample test(s)

input

2
4 2
1 4

output

4

input

3
1 6
3 4
2 5

output

15

把交换点和交换点之间的区间都当作点，进行离散化，数据量最多达到400000，然后就可以用树状数组处理了

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