program asfsdf;
var f,g:text;
n,i,m,s,x,y,st,sf,nr:longint;
a:array of array of longint;
viz,v,d:array of longint;
bufin,bufout:array[1..65000] of byte;
procedure dfs(nod:longint);
var k:longint;
begin
 viz[nod]:=1;
   for k:=1 to a[nod,0] do
      begin
         if viz[a[nod,k]]=0 then
            begin
              viz[a[nod,k]]:=1;
              dfs(a[nod,k]);
            end;
      end;
end;
begin
assign(f,'dfs.in'); reset(f);
assign(g,'dfs.out'); rewrite(g);
settextbuf(f,bufin);
settextbuf(g,bufout);
readln(f,n,m);
setlength(a,n+1,1);
setlength(viz,n+1);

   for i:=1 to m do
     begin
       readln(f,x,y);
       setlength(a[x],length(a[x])+1);;
       a[x,0]:=a[x,0]+1;
       a[x,a[x,0]]:=y;
     end;
   for i:=1 to n do
       if viz[i]=0 then
          begin
          nr:=nr+1;
          dfs(i);
          end;
       write(g,nr);
close(f);
close(g);
end.