import numpy as np
n,m=map(int,input().split())
z=np.zeros([m,n])
for i in range(n):
    b,c=map(int,input().split())
    z[b-1][c-1]+=1
for i in range(n):
    nonzero=np.where(z[:,i]!=0)[0]
    if(len(nonzero)!=0):
        p=nonzero[0]
        nonzero_r=nonzero[::-1][:-1]
        for idx in nonzero_r:
            z[p]+=z[idx]
            z=np.delete(z,idx,0)
print(m-z.shape[0])