/* -*- coding: utf-8 -*-
 *
 * 2403.cc:  No.2403 "Eight" Bridges of Kﾃｶnigsberg - yukicoder
 */

#include<cstdio>
#include<vector>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

using vi = vector<int>;

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 */

int dgs[MAX_N], gids[MAX_N], es[MAX_N];
UFT uft;
vi gvs[MAX_N];

/* subroutines */

/* main */

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

  uft.init(n);
  for (int i = 0; i < m; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u--, v--;
    dgs[u]++, dgs[v]--;

    int ru = uft.root(u), rv = uft.root(v);
    if (ru != rv) {
      int r = uft.merge(ru, rv);
      es[r] = es[ru] + es[rv] + 1;
    }
    else
      es[ru]++;
  }
  //for (int i = 0; i < n; i++) printf(" %d", dgs[i]); putchar('\n');

  fill(gids, gids + n, -1);
  int gn = 0, eg = 0;
  for (int i = 0; i < n; i++)
    if (uft.root(i) == i) {
      gids[i] = gn++;
      if (es[i] > 0) eg++;
    }
  for (int i = 0; i < n; i++)
    gvs[gids[uft.root(i)]].push_back(i);
  //printf(" gn=%d\n", gn);

  int sum = eg - 1;
  for (int gi = 0; gi < gn; gi++) {
    int dsum = 0;
    for (auto u: gvs[gi]) {
      if (dgs[u] > 0) dsum += dgs[u];
      //printf(" %d,%d", u, dgs[u]);
    }
    //putchar('\n');
    sum += max(0, dsum - 1);
  }

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