#747 ✧ ✦ Spark of Exam Luck ✦ ✧

Statement

Statement language

The second regular exam is approaching, and the $N$ students of Gyeonggi Science High School, numbered from $1$ to $N$ , are studying hard. The students have close friendships, and students who are friends help one another. There are $M$ friendship pairs in total.

One day, Seojun gives Mingi the ✧ ✦ Spark of Exam Luck ✦ ✧! Kindhearted Mingi wants to pass the spark on to many other students to help them do well on their exams. No student should feel left out while everyone around them receives a spark, so Mingi chooses two integers $L, R$ and wants every student numbered from to to receive one. Here, .

Input

The input is given in the following format.

$N\ M$ $a_1\ b_1$ $a_{2}$

Output

Print the answer to the problem on the first line.

Constraints

$1 \le N \le 10\,000$ .
$0 \le M \le 1\,000\,000$ .
().

Notes

$[L,R]$ denotes the range from $L$ to $R$ , inclusive.
Mingi is student number $-2$ , who does not study hard for exams.

Samples

Sample 1

Input

Output

9

Sample 2

Input

3 1
1 3

Output

3

Sample 3

Input

1 0

Output

1

Sample 4

Input

Output

6

Sample 5

Input

Output

21

Sample 6

Input

Output

58