N, K = map(int, input().split())
MOD = 998244353
S = set()
for i in range(K):
    l, r = map(int, input().split())
    for i in range(l, r + 1):
        S.add(i)

dp = [0] * N
dp[0] = 1
for i in range(1, N):
    for s in S:
        if s > i:
            continue
        dp[i] += dp[i - s]
print(dp[-1] % MOD)
