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