Problem Statement

There are $N$ cells arranged in a row, numbered $1, 2, \\ldots, N$ from left to right.

Tak lives in these cells and is currently on Cell $1$. He is trying to reach Cell $N$ by using the procedure described below.

You are given an integer $K$ that is less than or equal to $10$, and $K$ non-intersecting segments \[L_1, R_1\], \[L_2, R_2\], \\ldots, \[L_K, R_K\]. Let $S$ be the union of these $K$ segments. Here, the segment \[l, r\] denotes the set consisting of all integers $i$ that satisfy $l \\leq i \\leq r$.

• When you are on Cell $i$, pick an integer $d$ from $S$ and move to Cell $i + d$. You cannot move out of the cells.

To help Tak, find the number of ways to go to Cell $N$, modulo $998244353$.

Constraints

• $2 \\leq N \\leq 2 \\times 10^5$
• $1 \\leq K \\leq \\min(N, 10)$
• $1 \\leq L_i \\leq R_i \\leq N$
• \[L_i, R_i\] and \[L_j, R_j\] do not intersect ($i \\neq j$)
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$ $K$ $L_1$ $R_1$ $L_2$ $R_2$ $:$ $L_K$ $R_K$

Output

Print the number of ways for Tak to go from Cell $1$ to Cell $N$, modulo $998244353$.

Sample Input 1

5 2
1 1
3 4

Sample Output 1

4

The set $S$ is the union of the segment \[1, 1\] and the segment \[3, 4\], therefore $S = \\{ 1, 3, 4 \\}$ holds.

There are $4$ possible ways to get to Cell $5$:

• $1 \\to 2 \\to 3 \\to 4 \\to 5$,
• $1 \\to 2 \\to 5$,
• $1 \\to 4 \\to 5$ and
• $1 \\to 5$.

Sample Input 2

5 2
3 3
5 5

Sample Output 2

0

Because $S = \\{ 3, 5 \\}$ holds, you cannot reach to Cell $5$. Print $0$.

Sample Input 3

5 1
1 2

Sample Output 3

5

Sample Input 4

60 3
5 8
1 3
10 15

Sample Output 4

221823067

Note that you have to print the answer modulo $998244353$.