from atcoder.dsu import DSU
N,M=map(int,input().split())
uni=DSU(M)
color=[[] for i in range(N+1)]
for i in range(N):
    b,c=map(int,input().split())
    color[c].append(b-1)
for c in color:
    for i in range(len(c)-1):
        uni.merge(c[i],c[i+1])
ans=M
for i in range(M):
    if uni.leader(i)==i:
        ans-=1
print(ans)