#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

using namespace std;

ifstream f("dfs.in");
ofstream g("dfs.out");

int main() {
    int n,m,x,y,conex=0,nod,ok,i,j;
    f>>n>>m;
    vector<vector<int>>lista(n+1);
    stack<int>stiva;
    vector<int>viz(n+1,0);

    while(f){
        f>>x>>y;
        lista[x].push_back(y);
        lista[y].push_back(x);
    }

    for(j=1;j<=n;j++)
    {
        if(viz[j]==0){
            stiva.push(j);
            viz[j]=1;
            conex++;
        }
        while(!stiva.empty()){
            nod=stiva.top();
            ok=0;
            for(i=0;i<lista[nod].size();i++){
                if(viz[lista[nod][i]]==0){
                    stiva.push(lista[nod][i]);
                    viz[lista[nod][i]]=1;
                    ok=1;
                    break;
                }
            }
            if(ok==0){
                stiva.pop();
            }
        }
    }

    g<<conex;

    return 0;
}