N, K = map(int, input().split())
MOD = 998244353
S = []
for _ in range(K):
    S.append(tuple(map(int, input().split())))

dp = [0] * (N + 1)
dp[1] = 1

for i in range(2, N+1):
    for L, R in S:
        RR = i - L
        if RR <= 0:
            continue
        LL = max(1, i-R)
        dp[i] += sum(dp[LL:RR+1])
    dp[i] %= MOD

print(dp[N])
