using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Numerics;
using static System.Math;
using static Math2;
using static io;


class Program
{
    static void Main(string[] args)
    {
        var wrong_answer = new wrong_answer();
        wrong_answer.Solve();
    }
}

public class wrong_answer
{
    const int INF = 1 << 29;
    const long INFL = 1L << 60;
    const int MOD = 1000000007;
    const int MOD2 = 998244353;



    public void Solve()
    {
        var o = intm;
        var n = o[0];
        var m = o[1];

        var uf = new UnionFind(n);
        for(int i=0;i<m;++i){
            var oo=intm;
            uf.merge(oo[0]-1,oo[1]-1);
        }
        write(uf.count);

    }

}


public class UnionFind
{
    int _count;
    int[] par, sizes, rank;
    public UnionFind(int n)
    {
        _count = n;
        par = new int[n];
        sizes = new int[n];
        rank = new int[n];
        for (int i = 0; i < n; ++i)
        {
            par[i] = i;
            sizes[i] = 1;
            rank[i] = 0;
        }
    }
    int root(int x)
    {
        if (par[x] == x)
        {
            return x;
        }
        else return (par[x] = root(par[x]));
    }

    public bool merge(int x, int y)
    {
        x = root(x);
        y = root(y);
        if (x == y) return false;
        --_count;
        if (rank[x] < rank[y])
        {
            par[x] = y;
            sizes[y] += sizes[x];
        }
        else
        {
            par[y] = x;
            sizes[x] += sizes[y];
            if (rank[x] == rank[y]) ++rank[x];
        }
        return true;
    }
    public bool issame(int x, int y) => root(x) == root(y);
    public int count => _count;
    public bool ispar(int x) => x == root(x);
    public int getpar(int x) => root(x);
    public int size(int x) => sizes[root(x)];
}

public static class Math2
{
    public static long pow(long i, long n, long MOD = 1000000007)
    {
        long res = 1;
        while (n > 0)
        {
            if ((n & 1) != 0) res = res * i % MOD;
            i = i * i % MOD;
            n >>= 1;
        }
        return res;
    }

    public static long gcd(long i, long y)
    {
        while (y != 0)
        {
            var r = i % y;
            i = y;
            y = r;
        }
        return i;
    }

    public static long lcm(long i, long y)
    {
        return i * y / gcd(i, y);
    }

    public static BigInteger bgcd(BigInteger i, BigInteger y)
    {
        while (y != 0)
        {
            var r = i % y;
            i = y;
            y = r;
        }
        return i;
    }

    public static BigInteger blcm(BigInteger i, BigInteger y)
    {
        return i * y / bgcd(i, y);
    }

    public static Dictionary<long, int> primefactorization(long N)
    {

        var ret = new Dictionary<long, int>();

        for (long i = 2; i * i <= N; ++i)
        {
            int cnt = 0;
            while (N % i == 0)
            {
                cnt++;
                N /= i;
            }
            if (cnt != 0) ret[i] = cnt;

        }
        if (N >= 2) ret[N] = 1;

        return ret;

    }

    public static List<long> divisorenumrate(long N)
    {
        var ret = new List<long>();

        for (long i = 1; i * i <= N; ++i)
        {

            if (N % i == 0)
            {
                ret.Add(i);
                ret.Add(N / i);
            }

        }

        return ret;

    }

    public static void swap<T>(ref T a, ref T b)
    {
        var i = a;
        a = b;
        b = i;
    }
    public static void chmin<T>(ref T a, T b) where T : IComparable
    {
        if (a.CompareTo(b) > 0) a = b;
    }
    public static void chmax<T>(ref T a, T b) where T : IComparable
    {
        if (a.CompareTo(b) < 0) a = b;
    }

}

public static class io
{
    //in
    public static string str => Console.ReadLine();

    public static string[] strm => str.Split(' ');

    public static long[] longm => strm.Select(long.Parse).ToArray();
    public static int[] intm => strm.Select(int.Parse).ToArray();
    public static char[] charm => str.ToArray();
    public static double[] doublem => strm.Select(double.Parse).ToArray();
    public static long long1 => longm[0];
    public static int int1 => intm[0];
    public static char char1 => charm[0];
    public static double double1 => doublem[0];
    public static void write(string a) => Console.WriteLine(a);
    public static void write(params object[] i) => write(string.Join(" ", i));
    public static void write<T>(IEnumerable<T> a) => write(string.Join(" ", a));
    public static void yn(bool i) { if (i) write("Yes"); else write("No"); }

}


Measured memory_bytes: 18400