import numpy as np

mod = 998244353
n, k = map(int, input().split())
left = []
right = []
for _ in range(k):
  l, r = map(int, input().split())
  left.append(l)
  right.append(r)
dp = np.zeros(n, dtype=np.int)
dp[0] = 1
for i in range(n-1):
  for j in range(k):
    dp[i + left[j] : i + right[j] + 1] += dp[i]
    dp[i + left[j] : i + right[j] + 1] %= mod
print(dp[-1])