import java.io.*;
import java.util.*;
import java.math.*;

public class Main implements Runnable {
    String file = "template";
    ArrayList<Integer>[] edges;
    boolean[] visited;
    int gID;

    int dfs(int cur) {
        visited[cur] = true;
        int n = 1;
        for (int to : edges[cur]) {
            if (!visited[to]) {
                n += dfs(to);
            }
        }
        return n;
    }

    class Province implements Comparable<Province> {
        int size;
        int id;

        public Province(int size, int id) {
            this.size = size;
            this.id = id;
        }

        @Override
        public int compareTo(Province o) {
            if (size == o.size) {
                return id - o.id;
            }
            return size - o.size;
        }

    }

    @SuppressWarnings("unchecked")
    void solve() throws IOException {
        int n = nextInt();
        int m = nextInt();
        int k = nextInt();
        edges = new ArrayList[n];
        for (int i = 0; i < n; ++i) {
            edges[i] = new ArrayList<Integer>();
        }
        visited = new boolean[n];
        for (int i = 0; i < m; ++i) {
            int a = nextInt() - 1;
            int b = nextInt() - 1;
            edges[a].add(b);
            edges[b].add(a);
        }
        TreeSet<Province> comp = new TreeSet<Province>();
        int tot = 0;
        for (int i = 0; i < n; ++i) {
            if (!visited[i]) {
                int t = dfs(i);
                comp.add(new Province(t, gID++));
                tot += Math.min(k, t);
            }
        }
        int ans = 0;
        while (tot < (comp.size() - 1) * 2) {
            Province a = comp.pollFirst();
            Province b = comp.pollFirst();
            tot -= Math.min(k, a.size);
            tot -= Math.min(k, b.size);
            Province s = new Province(a.size + b.size, gID++);
            tot += Math.min(k, s.size);
            comp.add(s);
            ++ans;
        }
        out.println(ans);

    }

    public static void main(String[] args) {
        new Thread(new Main()).start();
    }

    BufferedReader br;
    PrintWriter out;
    StringTokenizer tok;

    public void run() {
        try {
            if (Boolean.getBoolean("SpbAU")) {
                br = new BufferedReader(new FileReader(file + ".in"));
                out = new PrintWriter(System.out);
            } else {
                br = new BufferedReader(new InputStreamReader(System.in));
                out = new PrintWriter(System.out);
            }
            tok = new StringTokenizer("");
            while (hasNext()) {
                solve();
            }
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    boolean hasNext() throws IOException {
        while (!tok.hasMoreElements()) {
            String line = br.readLine();
            if (line == null) {
                return false;
            }
            tok = new StringTokenizer(line);
        }
        return true;
    }

    String next() throws IOException {
        if (hasNext()) {
            return tok.nextToken();
        }
        System.err.println("Nom more tokens");
        System.exit(1);
        return "";
    }

    int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

    long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }
}