var a:array[1..1000,1..1000] of byte;
    v:array[1..200000] of byte;
    nr,n,m,i,x,y:longint;

procedure df(k:integer);
var i:integer;
begin
for i:=1 to n do
if (v[i]=0) and (a[k,i]=1) then
begin
v[i]:=1;
df(i);
end;
end;

begin
assign(input,'dfs.in');reset(input);
assign(output,'dfs.out');rewrite(output);
readln(n,m);
for i:=1 to m do
begin
readln(x,y);
a[x,y]:=1;
a[y,x]:=1;
end;
for i:=1 to n do
if v[i]=0 then
begin
v[i]:=1;
inc(nr);
df(i);
end;
write(nr);
end.