#include <bits/stdc++.h>
using namespace std;

/* thx for Kohenyan (Debug) */
struct UnionFind {
    vector<int> par, rank;
    //init size N
    UnionFind(int N) {
        par.assign(N, int()), rank.assign(N, int());
        for(int i = 0; i < N; i++) {
            par[i] = i;
            rank[i] = 1;
        }
    }

    // Find Loot
    int find(int x) {
        if(par[x] == x) {
            return x;
        }else {
            return par[x] = find(par[x]);
        }
    }

    // Unite x and y
    void unite(int x, int y) {
        x = find(x);
        y = find(y);
        if(x == y) return;

        if(rank[x] < rank[y]) {
            par[x] = y;
            rank[y] += rank[x];
        }else {
            par[y] = x;
            rank[x] += rank[y];
        }
    }

    // isSametree?
    bool same(int x, int y) {
        return find(x) == find(y);
    }

    // size of x's set
    int size(int x) {
        return rank[find(x)];
    }
};

int main() {
    int N, M;
    cin >> N >> M;
    vector A(M, 0), B(M, 0);
    for(int i = 0; i < M; i++) cin >> A[i] >> B[i];
    UnionFind UF(2*N);
    for(int i = 0; i < M; i++) UF.unite(A[i]-1, B[i]-1);
    int ans(N);
    vector seen(2*N, false);
    for(int i = 0; i < 2*N; i++) {
        if(seen[UF.find(i)]) continue;
        else {
            ans -= UF.size(i) / 2;
            seen[UF.find(i)] = true;
        }
    }
    cout << ans << endl;
    return 0;
}