/* -*- coding: utf-8 -*-
 *
 * 2418.cc:  No.2418 情報通だよ!Nafmoくん - yukicoder
 */

#include<cstdio>
#include<vector>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 100000;
const int MAX_N2 = MAX_N * 2;

/* typedef */

struct UFT {
  vector<int> links, ranks, sizes;
  UFT() {}

  void init(int n) {
    links.resize(n);
    for (int i = 0; i < n; i++) links[i] = i;
    ranks.assign(n, 1);
    sizes.assign(n, 1);
  }

  int root(int i) {
    int i0 = i;
    while (links[i0] != i0) i0 = links[i0];
    return (links[i] = i0);
  }

  int rank(int i) { return ranks[root(i)]; }
  int size(int i) { return sizes[root(i)]; }
  bool same(int i, int j) { return root(i) == root(j); }

  int merge(int i0, int i1) {
    int r0 = root(i0), r1 = root(i1), mr;
    if (r0 == r1) return r0;
    if (ranks[r0] == ranks[r1]) {
      links[r1] = r0;
      sizes[r0] += sizes[r1];
      ranks[r0]++;
      mr = r0;
    }
    else if (ranks[r0] > ranks[r1]) {
      links[r1] = r0;
      sizes[r0] += sizes[r1];
      mr = r0;
    }
    else {
      links[r0] = r1;
      sizes[r1] += sizes[r0];
      mr = r1;
    }
    return mr;
  }
};

/* global variables */

UFT uft;

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  int n2 = n * 2;
  uft.init(n2);

  for (int i = 0; i < m; i++) {
    int a, b;
    scanf("%d%d", &a, &b);
    a--, b--;
    uft.merge(a, b);
  }

  int c = 0;
  for (int u = 0; u < n2; u++)
    if (u == uft.root(u)) c += uft.size(u) / 2;

  printf("%d\n", n - c);
  return 0;
}