n, k = map(int, input().split())
lr = [list(map(int, input().split())) for _ in range(k)]
mod = 998244353

dp = [0] * n
dp[0] = 1

acc = 0

for i in range(1, n):
    for l, r in lr:
        if i - l >= 0:
            acc += dp[i - l]
            acc %= mod
        if i - r - 1 >= 0:
            acc -= dp[i - r - 1]
            acc %= mod
        dp[i] = acc

print(dp[-1])
