#include <bits/stdc++.h>
#pragma warning(disable : 4786)
#pragma warning(disable : 4996)
using namespace std;
struct Edge {
  int from, to, cap, flow, index;
  Edge(int from, int to, int cap, int flow, int index)
      : from(from), to(to), cap(cap), flow(flow), index(index) {}
};
const int INF = 2000000000;
struct Dinic {
  int N;
  vector<vector<Edge> > G;
  vector<Edge *> dad;
  vector<int> Q;
  Dinic(int N) : N(N), G(N), dad(N), Q(N) {}
  void AddEdge(int from, int to, int cap) {
    G[from].push_back(Edge(from, to, cap, 0, G[to].size()));
    if (from == to) G[from].back().index++;
    G[to].push_back(Edge(to, from, 0, 0, G[from].size() - 1));
  }
  long long BlockingFlow(int s, int t) {
    fill(dad.begin(), dad.end(), (Edge *)NULL);
    dad[s] = &G[0][0] - 1;
    int head = 0, tail = 0;
    Q[tail++] = s;
    while (head < tail) {
      int x = Q[head++];
      for (int i = 0; i < G[x].size(); i++) {
        Edge &e = G[x][i];
        if (!dad[e.to] && e.cap - e.flow > 0) {
          dad[e.to] = &G[x][i];
          Q[tail++] = e.to;
        }
      }
    }
    if (!dad[t]) return 0;
    long long totflow = 0;
    for (int i = 0; i < G[t].size(); i++) {
      Edge *start = &G[G[t][i].to][G[t][i].index];
      int amt = INF;
      for (Edge *e = start; amt && e != dad[s]; e = dad[e->from]) {
        if (!e) {
          amt = 0;
          break;
        }
        amt = min(amt, e->cap - e->flow);
      }
      if (amt == 0) continue;
      for (Edge *e = start; amt && e != dad[s]; e = dad[e->from]) {
        e->flow += amt;
        G[e->to][e->index].flow -= amt;
      }
      totflow += amt;
    }
    return totflow;
  }
  long long GetMaxFlow(int s, int t) {
    long long totflow = 0;
    while (long long flow = BlockingFlow(s, t)) totflow += flow;
    return totflow;
  }
};
int main() {
  int n, m;
  scanf("%d %d", &n, &m);
  Dinic A(1 + n + m + m + m + 1);
  int src = 0;
  int sink = 1 + n + m + m + m;
  for (int i = 1; i <= n; i++) A.AddEdge(src, i, 1);
  int sec = n;
  int thir = n + m;
  int forth = n + m + m;
  for (int i = 1; i <= m; i++) A.AddEdge(forth + i, sink, 1);
  for (int i = 1; i <= n; i++) {
    int l, r;
    scanf("%d %d", &l, &r);
    if (l) A.AddEdge(i, thir + l, 1);
    if (r) A.AddEdge(i, sec + r, 1);
  }
  for (int i = 1; i <= m; i++) {
    A.AddEdge(sec + i, forth + i, 1);
    A.AddEdge(thir + i, forth + i, 1);
  }
  int flow = A.GetMaxFlow(src, sink);
  printf("%d\n", n - flow);
  return 0;
}
