N,H=map(int, input().split())
C=[0]*(10**6+10) 
for i in range(N):
  a,b=map(int, input().split())
  C[a]+=1
  C[b+1]-=1
  
ans=0
now=0
for c in C:
  now+=c 
  ans=max(ans,now)
print(ans)