N, K = map(int, input().split())
mod = 998244353
D = []
dp = [0] * (N+1)
for i in range(K):
    L, R = map(int, input().split())
    D.append([L, R])

dp[0] = 1
a = 0
for i in range(N):
    a += dp[i]
    a %= mod
    for d in D:
        if i + d[0] > N:
            continue
        dp[i + d[0]] += a
        if i + d[1] + 1 > N:
            continue

        dp[i + d[1] + 1] -= a

print(dp[N-1])

