def resolve():
    n, k = map(int, input().split())
    mod = 998244353
    dp = [0] * (3*n)
    imos = [0] * (3*n)
    lr = []
    for i in range(k):
        l, r = map(int, input().split())
        lr.append((l, r+1))
    for l, r in lr:
        imos[l] = 1
        imos[r] = -1
    for i in range(1, n+1):
        dp[i] = (dp[i-1] + imos[i]) %mod
        for l, r in lr:
            imos[min(i+l, n+2)] += dp[i]
            imos[min(i+r, n+2)] += -1*dp[i]
    print(dp[n-1]%mod)

resolve()