You are given \(10^6\) boxes that are numbered from \(1\) to \(10^6\). The value of each box is equal to its number.
There are \(N\) ranges and every range consists of two integers \(L\) and \(R\) denoting that the value of box in the range \([L,R] \) will turn out to be zero.
Find the sum of values of all boxes from \(1\) to \(10^6\) .

Note: The ranges may overlap.

Input format

First line: Integer \(N\)
Next N lines: Two space-separated integers \(L\) and \(R\)

Output format
Print a single integer denoting the answer.

Constraints
\(0 ≤ N ≤ 10^5 \)
\(1 ≤ L ≤ R ≤ 10^6 \)