AT_abc469_d [ABC469D] The Big Two

There is a game with $ N $ players $ 1,2,\dots,N $ . This game is played in a format where two players face each other one-on-one. A tournament among the $ N $ players was held $ M $ times, and the two players $ A_m $ and $ B_m $ advanced to the final of the $ m $ -th tournament. Find the number of pairs of integers $ x $ and $ y $ satisfying the following conditions. - $ 1 \leq x \lt y \leq N $ - In every tournament, at least one of players $ x $ and $ y $ advanced to the final.

The input is given from Standard Input in the following format: > $ N $ $ M $ $ A_1 $ $ B_1 $ $ A_2 $ $ B_2 $ $ \vdots $ $ A_M $ $ B_M $

Output the answer in one line.

### Sample Explanation 1 The conditions are satisfied when $ (x,y)=(2,3) $ , and not satisfied otherwise. For example, in the fourth tournament, neither player $ 1 $ nor player $ 4 $ advanced to the final, so $ (x,y)=(1,4) $ does not satisfy the conditions. ### Sample Explanation 2 There are two pairs $ (x,y) $ satisfying the conditions: $ (1,2) $ and $ (1,4) $ . ### Constraints - $ 2 \leq N \leq 2 \times 10^5 $ - $ 1 \leq M \leq 2 \times 10^5 $ - $ 1 \leq A_i \lt B_i \leq N $ - All input values are integers.