# include <fstream>

using namespace std;

ifstream f("dfs.in");
ofstream g("dfs.out");

#define MAXN 100001;

int N,M,A[MAXN][MAXN],viz[MAXN],c=1;

void citire()
{
f>>N>>M;
while (!f.eof())
{
int x,y;
f>>x>>y;
a[x][y]=1;
a[y][x]=1;
f.close();
}
}

void DFS(int x,int&c)
{
viz[x]=1;
for (int i=1; i<=N; i++)
if(a[x][i]==1 && viz[i]==0)
{
c++;
DFS(i);
}
}

int main()
{
citire();
DFS(1,c);
if(c!=1)
g<<c;
g.close();
return 0;
}