#include<iostream.h>
#include<fstream.h>
int a[10][101],v[101],n,k,c=1,m;
void citire(){
int i,j,k;
ifstream f("dfs.in");
f>>n>>m;
for(k=1;k<=m;k++){
	f>>i>>j;
	a[i][j]=a[j][i]=1;
}
	f.close();


}
void parcurgere(int i,int c)
{
int j;
v[i]=c;
for(j=1;j<=n;j++)
	if(a[i][j]==1&&v[j]==0)
		parcurgere(j,c);
	

}
int main(){
int i,j;
	citire();
for(i=1;i<=n;i++)
	if(v[i]==0)
	{
		parcurgere(i,c);
	c++;
	}
	ofstream g("dfs.out");
	
g<<c-1<<"\n";
g.close();
}