#include <bits/stdc++.h>
#define INfile "dfs.in"
#define OUTfile "dfs.out"
#define LMax 20000

using namespace std;

ifstream fin(INfile);
ofstream fout(OUTfile);

pair<int,int> mat[LMax];
int x,y,n, m;
int v[LMax],nrcmp;

bool ifexist(int elem)
{
    for(int i=1; i<=n; ++i)
        if(mat[i].second==elem)
            return true;
    return false;
}

bool ifexist2(int elem)
{
    for(int i=1; i<=n; ++i)
        if(mat[i].first==elem)
            return true;
    return false;
}

void dfs(int i)
{
    for (int j = 1; j <= n; ++j)
        if (ifexist2(i)==true && ifexist(j)==true && v[j] == 0)
        {
            v[j] = 1;
            dfs(j);
        }
}
int main()
{
    fin >> n >> m;
    for(int i=1; i<=m; ++i)
    {
       fin>>mat[i].first>>mat[i].second;
    }
    for (int i = 1; i <= n; ++i)
    {
        if (v[i] == 0)
        {
            dfs(i);
            nrcmp++;
        }
    }
    fout<<nrcmp;
    return 0;
}