N, K = map(int, input().split())
S = []

for _ in range(K):
  L, R = map(int, input().split())
  S.extend(range(L,R+1))
  
S.sort()

DP =[0]*N
DP[0] = 1

for i in range(N-1):
  for j in S:
    
    if i+j<N:
      DP[i+j] += DP[i]
    else:
      break

print(DP[-1]%998244353)