#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int INF = (int)1e9;
const long long LINF = (long long)1e18;
const long double PI = acos((long double)-1);
const long double EPS = 1e-9;
long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
void setmin(T& a, T val) {
  if (a > val) a = val;
}
template <class T>
void setmax(T& a, T val) {
  if (a < val) a = val;
}
void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
const int maxn = 100010;
int n, m;
int dj[maxn];
int sz[maxn];
int tot[maxn];
void init() {
  for (int i = (0); i < (n); i++) dj[i] = i, sz[i] = 1;
}
int find(int u) { return dj[u] == u ? dj[u] : dj[u] = find(dj[u]); }
void join(int u, int v) {
  int p = find(u);
  int q = find(v);
  if (p != q) {
    dj[p] = q;
    tot[q] += tot[p];
    sz[q] += sz[p];
  }
  tot[q]++;
}
void solve() {
  cin >> n >> m;
  init();
  for (int i = (0); i < (m); i++) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    join(u, v);
  }
  int ans = 0;
  for (int i = (0); i < (n); i++) {
    if (dj[i] == i) {
      if (tot[i] < sz[i]) {
        ans++;
      }
    }
  }
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  solve();
  return 0;
}
