def main():
    n, k = map(int, input().split())
    lr = []
    for _ in range(k):
        lr.append(tuple(map(int, input().split())))
    mod = 998244353
    
    dp = [0]*n
    dp[0] = 1
    
    acc = [0]*n
    acc[0] = 1
    
    for i in range(1, n):
        for l, r in lr:
            if 0 <= i-r and i-l < i:
                dp[i] += acc[i-l]-acc[i-r-1]
            elif i-r < 0 and i-l < i:
                dp[i] += acc[i-l]
            elif i-r < 0 and i <= i-l:
                dp[i] += acc[i-1]
            elif 0 < i-r and i <= i-l:
                dp[i] += acc[i-1]-acc[i-r-1]
        acc[i] = acc[i-1]+dp[i]
    
    print(dp[-1]%mod)


main()