program parcurgere;
type mat=array[1..240,1..240] of byte;
     vec=array[1..240] of byte;
var a:mat;
    b:vec;
    t:boolean;
    f,g:text;
    k,nod,n,m,i,l,c:integer;
procedure df(nod:integer);
var i:integer;
begin
b[nod]:=1;
for i:=1 to n do if (a[nod,i]=1) and (b[i]=0) then
df(i);
end;
begin
assign(f,'dfs.in');assign(g,'dfs.out');reset(f);rewrite(g);
readln(f,n,m);
k:=0;
for i:=1 to m do begin
readln(f,l,c);
a[l,c]:=1;
a[c,l]:=1;
end;
t:=true;
while t do begin
t:=true;
for i:=1 to n do if b[i]=0 then begin
              df(i);k:=k+1;
              t:=false;end;
              end;
write(g,k);close(g);close(f);
end.