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 $*p*_{*i*} > *p*_{*j*}$.

Input

The first line contains a single integer $*n*$ ($1 ≤ *n* ≤ 10^{5}$) — the number of swap operations applied to the sequence.

Each of the next $*n*$ lines contains two integers $*a*_{*i*}$ and $*b*_{*i*}$ ($1 ≤ *a*_{*i*}, *b*_{*i*} ≤ 10^{9}$, $*a*_{*i*} ≠ *b*_{*i*}$) — the arguments of the swap operation.

Output

Print a single integer — the number of inversions in the resulting sequence.

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 $(3, 4)$.