#include <fstream>
#include <vector>

using namespace std;

void dfs(int v,vector< vector<int> >& graph, vector<bool>& visited) {
	visited[v] = 1;
	for (int& w : graph[v]) {
		if (!visited[w])  {
			dfs(w, graph, visited);
		}
	}
}

int main()
{
	ifstream cin("dfs.in");
	ofstream cout("dfs.out");
	int n, m, src;
	cin >> n >> m >> src;
	vector< vector<int> > graph(n);
	vector<bool> visited(n);
	for (int i = 0; i < m; i++) {
		int a, b;
		cin >> a >> b;
		graph[--a].push_back(--b);
		graph[b].push_back(a);
	}

	int ans = 0;

	for (int i = 0; i < n; i++) {
		if (!visited[i]) {
			dfs(i, graph, visited);
			ans++;
		}
	}
	cout << ans;
	return 0;
}