N,H=map(int,input().split())
Acnt=[0 for _ in range(H+1)]
Bcnt=[0 for _ in range(H+2)]
for _ in range(N):
    A,B=map(int,input().split())
    Acnt[A]+=1
    Bcnt[B+1]+=1
ans=0
now=0
for i in range(H):
    now+=Acnt[i]-Bcnt[i]
    ans=max(ans,now)
print(ans)