P=998244353
N,K=map(int, input().split())
LR=[list(map(int, input().split())) for _ in range(K)]

s=[0 for _ in range(N+1)]
s[1]=1
for i in range(1,N):
  s[i+1] = s[i]
  for l,r in LR:
    s[i+1]+=(s[max(0,i-l+1)]-s[max(0,i-r)])%P
    s[i+1]%=P
print((s[N]-s[N-1])%P)