mod = 998244353
n, k = map(int, input().split())
lr = [list(map(int, input().split())) for i in range(k)]
for i in range(k):
    lr[i][1] += 1
dp = [0] * n
dp[0] = 1
for i in range(1, n):
    dp[i] += dp[i - 1]
    if i == 1:
        dp[1] = 0
    for l, r in lr:
        if i - l >= 0:
            dp[i] += dp[i - l]
        if i - r >= 0:
            dp[i] -= dp[i - r]
    dp[i] %= mod
print(dp[n - 1])