N, K = map(int, input().split())
mod = 998244353

LR = [tuple(map(int, input().split())) for _ in range(K)]
LR.sort()

dp = [0] * (N + 1)
dp[1] = 1
for i in range(1, N):
    if dp[i] <= 0:
        continue
    for L, R in LR:
        for d in range(L, R + 1):
            if i + d < N + 1:
                dp[i + d] += dp[i]
                dp[i + d] %= mod

print(dp[N])
