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
$0 ≤ N ≤ 10^5$
$1 ≤  L ≤ R ≤ 10^6$