#include <fstream>
#include <vector>
#define NMax 100010
#define MMax 200010

using namespace std;
ofstream fout("dfs.out");
ifstream fin("dfs.in");

vector <int> v[NMax];
bool viz[NMax];
int n,m;

void dfs(int nod)
{
    viz[nod]=1;

    for(int i=0;i<v[nod].size();i++)
    {
        if(viz[v[nod][i]]==0)
        {
            dfs(v[nod][i]);
        }
    }
}

void act(int &nod)
{
    int i=nod+1;
    while(viz[i]==1)
    {
        i++;
    }

    nod=i;
}

int main()
{
    int in=1,nr=0,x=0,y=0;

    fin>>n>>m;

    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }

    while(in<=n)
    {
        dfs(in);
        act(in);
        nr++;
    }

    fout<<nr;

    return 0;
}