#include <fstream>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <queue>

using namespace std;

template <class T>
class graph {
    unordered_map<T, vector<T>> neighbors;
    unordered_set<T> nodes;

    void depth_first_search(T node, unordered_set<T>& visited) {
	visited.insert(node);

	for (auto next : neighbors[node]) {
	    if (visited.find(next) == visited.end()) {
		depth_first_search(next, visited);
	    }
	}
    }
    
public:
    template <class Iterator>
    graph(Iterator begin, Iterator end):
	nodes(begin, end) {}

    void add_edge(T src, T dst) {
	neighbors[src].push_back(dst);
    }

    unordered_map<T, int> breadth_first_search(T node) {
	unordered_map<T, int> result;
	unordered_set<T> visited;
	queue<T> q;

	result[node] = 0;
	q.push(node);
	visited.insert(node);
	while (!q.empty()) {
	    auto x = q.front(); q.pop();

	    for (auto next : neighbors[x]) {
		if (visited.find(next) == visited.end()) {
		    visited.insert(next);
		    result[next] = result[x] + 1;
		    q.push(next);
		}
	    }
	}

	for (auto other : nodes) {
	    if (other != node && result[other] == 0)
		result[other] = -1;
	}

	return result;
    }

    int connected_components() {
	unordered_set<T> visited;

	int result = 0;
	for (auto node : nodes) {
	    if (visited.find(node) == visited.end()) {
		result += 1;
		depth_first_search(node, visited);
	    }
	}

	return result;
    }
};

int main() {
    ifstream fin("dfs.in");
    ofstream fout("dfs.out");

    int n, m;
    fin >> n >> m;
    vector<int> nodes;
    for (int i = 1; i <= n; ++i) {
	nodes.push_back(i);
    }
    graph<int> G(nodes.begin(), nodes.end());
    for (int i = 0; i < m; ++i) {
	int src, dst;
	fin >> src >> dst;
	G.add_edge(src, dst);
	G.add_edge(dst, src);
    }

    fout << G.connected_components() << endl;

    return 0;
}