N, K = [int(v) for v in input().split()]

link = []
for k in range(K):
    L, R = [int(v) for v in input().split()]

    for i in range(L, R+1):
        link.append(i)

link.sort()
count = [1]

for i in range(1, N):
    v = 0
    for l in link:
        if i < l:
            break
        v = (v + count[i - l]) % 998244353
    count.append(v)

print(count[-1])
