#!/usr/bin/python3
# -*- coding: utf-8 -*-
import numpy as np
n, k = map(int, input().split())
s_list = []
a_list = np.zeros((n + 1) * 2, dtype=int)
a_list[1] = 1
for i in range(k):
    l, r = map(int, input().split())
    s_list.append([l, r + 1])

for i in range(1, n):
    a_list[i] %= 998244353
    if a_list[i] == 0:
        continue
    for l, r in s_list:
        if i + l > n:
            continue
        if i + r > n + 1:
            a_list[(i+l):(n+1)] += a_list[i]
        else:
            a_list[(i+l):(i+r)] += a_list[i]
print(a_list[n] % 998244353)

