N,H = map(int,input().split())
S = [0] * (H + 1)
for _ in range(N):
	a,b = map(int,input().split())
	S[a] += 1
	S[b + 1] -= 1
ans = 0
for i in range(H):
	S[i+1] += S[i]
	if S[i] > ans:ans = S[i]
print(ans)