+ محدودیت زمان: ۱ ثانیه + محدودیت حافظه: ۲۵۶ مگابایت --- Majid has a binary string of length $n$ with only 1 values. One morning, his niece accidentally finds this string and starts destroying it. She destroys the string in $t$ steps. The niece first chooses a sequence of integers: $1 \leq a_1 \leq a_2 \leq \dots \leq a_t \leq n$. Then, in the $i$-th step, she selects the first $a_i$ bits and destroys this part as follows: - First, she negates all the selected bits. - Then, she reverses the order of the selected part. To be more precise, if the binary string before the $i$-th step is as follows: $$S = s_1 s_2, \dots, s_n$$ The binary string after the $i$-th step will be as follows, where $\bar{s}_i$ represents the negation of bit $s_i$: $$S = \bar{s}_{a_i}, \bar{s}_{a_i-1}, \dots, \bar{s}_1, s_{a_i+1}, \dots, s_n$$ Majid wants to restore the string to its initial state using his superpower. Each time Majid uses his superpower, he chooses two numbers $1 \leq l \leq r \leq n$. Then, magically, all the bits in positions from $l$ to $r$ inclusive are negated. This interval includes the bits at positions $l$ and $r$ themselves. The positions of the bits are considered from left to right, and the leftmost bit has a position of $1$. Help Majid restore the string to its initial state with the fewest number of uses of his superpower. # ورودی The first line of the input consists of two integers $n$ $(1 \leq n \leq 10^{18})$ and $t$ $(1 \leq t \leq 10^5)$ separated by a space, which is the length of the string and the number of steps of string destruction, respectively. The second line contains a sequence of integers $a_1, a_2, \dots, a_t$ $(1 \leq a_i \leq n)$, chosen by the niece. # خروجی Print $k$, the minimum number of times Majid needs to use his superpower in the first line. Then, in the $(i+1)$th line $(1 \leq i \leq k)$ of the output, print the interval that Majid chooses in his use of superpower as two numbers separated by a space, in ascending order. ## ورودی نمونه 1 ``` 5 2 2 5 ``` ## خروجی نمونه 1 ``` 1 1 3 ``` ## ورودی نمونه 2 ``` 5 2 3 3 ``` ## خروجی نمونه 2 ``` 0 ```