DFS+BFS

#include <bits/stdc++.h>
#define ll long long

using namespace std;

const int maxn= 1e5+5;

int n,m;
int check[maxn];
vector <int> e[maxn];
stack<int> s;
queue <int> q;
int ans=0;

/*void dfs(int x){
    //while(!s.empty()) s.pop();
    s.push(x);
    check[x]=1;
    while(!s.empty()){
        int u=s.top();
        s.pop();
        //cout<<u<<" ";
        for (int v: e[u])
            if (check[v]==0){
               check[v]=1;
               s.push(v);
            }
    }
}*/

void bfs(int x)
{
    q.push(x);
    check[x]=1;
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        //cout<<u<<" ";
        for (int v: e[u])
            if (check[v]==0)
            {
                check[v]=1;
                q.push(v);
            }
    }
}

int main()
{
    cin>>n>>m;
    for (int i=1; i<=m; i++)
    {
        int u,v;
        cin>>u>>v;
        e[u].push_back(v);
        e[v].push_back(u);
    }
    //dfs(1);
    //bfs(1);
    for (int i=1; i<=n; i++)
    {
        if (check[i]==0)
        {
            ans++;
            dfs(i);
            //bfs(i);
        }
    }
    cout<<ans<<endl;
    return 0;
}