#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");
const int N=100001;
vector<int> a[N];
int n,count=0;
bool viz[N];
void citire()
{
    int x,y,m;
    f>>n>>m;
    for(int i=0; i<=m; ++i)
    {
        f>>x>>y;
        a[x].push_back(y);
        a[y].push_back(x);
    }
}
void dfs(int x)
{
    int y;
    viz[x]=true;
    for( size_t i=0; i<a[x].size(); ++i)
    {
        y = a[x][i];
        if (!viz[y])
            {
                ++count;
                dfs(y);
            }
    }
}
int main()
{
    citire();
    for(int i=1; i<n; ++i)
        if (!viz[i])
            dfs(i);
    g<<count;
    return 0;
}