n,k = map(int,input().split())
lr = []
for _ in range(k):
  lr.append(list(map(int,input().split())))
print(lr)
imos = [0 for _ in range(n)]
imos[0] = 1
imos[1] = -1
now = 0
mod = 998244353
for i in range(n):
    now += imos[i]
    now %= mod
    #print(now)
    for j in range(k):
        try:
            imos[i+lr[j][0]] += now
            imos[i+lr[j][0]] %= mod
        except:
            pass
        try:
            imos[i+lr[j][1]+1] -= now
            imos[i+lr[j][1]+1] %= mod
        except:
            pass
    #print(imos)
print(now)