n,k = map(int,input().split())
st = []
for i in range(k):
  x,y = map(int,input().split())
  st.append((x,y))
total = [1]
 
for i in range(1,n):
  s = 0
  for (x,y) in st:
    if i > y:
      s = (s + total[i-x] - total[i-y-1]) % 998244353
    elif i >= x:
      s = (s + total[i-x]) % 998244353
  total.append((s+total[-1]) % 998244353)   
  
print((total[-1]-total[-2]) % 998244353)
  
  
    
  