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

using namespace std;

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

struct nod
{
    int val;
    nod *next;
};
nod *l[100001];
int n,m;
int fr[100001];

void adauga(int i, int j)
{
    if(l[i]==NULL)
    {
        l[i]=new nod;
        l[i]->val=j;
        l[i]->next=NULL;
    }
    else
    {
        nod *p=new nod;
        p->val=j;
        p->next=l[i];
        l[i]=p;
    }
}

void citire()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        adauga(x,y);
        adauga(y,x);
    }
}

void dfs(int s, int &cnt)
{
    stack<int> st;
    st.push(s);
    while(!st.empty())
    {
        int top=st.top();
        st.pop();
        bool ok=true;
        for(nod *p=l[top];p!=NULL;p=p->next)
        {
            if(fr[p->val]==0)
            {
                ok=false;
                fr[p->val]=fr[top]+1;
                st.push(p->val);
            }
        }
        if(ok==true) cnt++;
    }
}

void rezolva(int &cnt)
{
    cnt=0;
    for(int i=1;i<=n;i++)
    {
        if(fr[i]==0 and l[i]!=NULL)
        {
            dfs(i,cnt);
        }
    }
}

int main()
{
    int cnt=0;
    citire();
    rezolva(cnt);
    fout<<cnt;
    return 0;
}