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

mod = 998244353

S = []
for _ in range (K):
    l,r = map(int,input().split())
    for i in range (l,r+1):
        S.append(i)

S.sort()

ans = [0]*N
ans[0] = 1

for i in range (1,N):
    for j in S:
        if i-j < 0:
            break
        else:
            ans[i] += ans[i-j]
            ans[i] %= mod


print(ans[N-1])
