#include <bits/stdc++.h>

using namespace std;

ifstream F("dfs.in");
ofstream G("dfs.out");

int n, m, x, y, grd[100005], L[100005], g[200005], K;
bitset<100005> v;
vector<pair<int, int> > a;

void dfs(int nod){
    v[nod]=1;
    int x = grd[nod-1];
    int y = grd[nod];
    for(int i = 1; i <= n; ++ i){
        if(!v[i] && binary_search(g+x, g+y, i)){
            dfs(i);
        }
    }
}

int main()
{
    F >> n >> m;
    for(int i = 1; i <= m; ++ i){
        F >> x >> y;
        grd[x]++; grd[y]++;
        a.push_back({x, y});
    }
    for(int i = 1; i <= n; ++ i){
        grd[i]+=grd[i-1];
        L[i]=grd[i-1];
    }
    for(int i = 1; i <= m; ++ i){
        x=a[i-1].first;
        y=a[i-1].second;
        g[L[x]++]=y;
        g[L[y]++]=x;
    }
    for(int i = 1; i <= n; ++ i){
        x = grd[i-1];
        y=grd[i];
        sort(g+x, g+y);
    }
    for(int i = 1; i <= n; ++ i){
        if(!v[i]){
            dfs(i);
            K++;
        }
    }
    G << K;
    return 0;
}