n,k = map(int,input().split())
st = set([])
for i in range(k):
  x,y = map(int,input().split())
  for z in range(x,y+1):
    st.add(z)
ans = [1]
for i in range(1,n):
  s = 0
  for x in st:
    if i >= x:
      s = s + ans[i-x]
  ans.append(s % 998244353)   
  
print(ans[-1])  
  
  
    
  