N,K=map(int,input().split())
x=998244353
S=[]
for i in range(K):
    l,r=map(int,input().split())
    for j in range(l,r+1):
      S.append(j)
S=list(set(S))
dp=[0 for i in range(N)]
for i in range(len(S)):
    dp[S[i]]=1
for i in range(N):
    for j in range(len(S)):
        if(i-S[j]>0):
            dp[i]+=dp[i-S[j]]
            dp[i]=dp[i]%x
print(dp[-1])
