#include <fstream>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");
struct graf{int x,y;}v[100001];
int n,s,m,viz[100001],prim,ultim,p,este,i,k;
void citire()
{f>>n>>m;
 for(int i=1;i<=m;i++)f>>v[i].x>>v[i].y;
}
void dfs(int nod)
{viz[nod]=1;
 for(int i=1;i<=m;i++)
    if(v[i].x==nod&&viz[v[i].y]==0)dfs(v[i].y);
        else if(v[i].y==nod&&viz[v[i].x]==0)dfs(v[i].x);
}
int main()
{
    citire();
    este=1;
    while(1)
    {for(i=1;i<=n;i++)if(viz[i]==0)break;
     if(i==n+1)break;
     dfs(i);;
     k++;
    }
    g<<k;
    return 0;
}