Score : 100 points
You have N cups and 1 ball.
The cups are arranged in a row, from left to right.
You turned down all the cups, then inserted the ball into the leftmost cup.
Then, you will perform the following Q operations:
Since you are a magician, you can cast a magic described below:
The magic can be cast before the first operation, between two operations, or after the last operation, but you are allowed to cast it at most once during the whole process.
Find the number of cups with a possibility of containing the ball after all the operations and possibly casting the magic.
The input is given from Standard Input in the following format:
N Q A_1 B_1 A_2 B_2 : A_Q B_Q
Print the number of cups with a possibility of eventually containing the ball.
10 3 1 3 2 4 4 5
4
20 3 1 7 8 20 1 19
5