N, K = map(int, input().split())

DP = [0]*(N+1)
DP[1] = 1

S = []
for i in range(K):
    S.append(list(map(int, input().split())))

for i in range(2, N+1):
    for l, r in S:
            DP[i] += (DP[max(i-l, 0)] - DP[max(i-r-1, 0)])
    DP[i] += DP[i-1]
    DP[i] %= 998244353

print(DP[N]%998244353)