N, K = map(int,input().split())
LR = [tuple(map(int,input().split())) for _ in range(K)]
d = [0]*N
d[0] = 1
MOD = 998244353
for i in range(N-1):
    x = d[i]
    d[0] = 0
    for k in range(K):
        L, R = LR[k]
        if i+L < len(d):
            d[i+L] += x
            d[i+L] %= MOD
        if i+R+1 < len(d):
            d[i+R+1] -= x
            d[i+R+1] %= MOD
    d[i+1] += d[i]
    d[i+1] %= MOD
print(d[-1] % MOD)