var i,j,k,l,m,n:longint; a:array[1..100000,1..100000] of longint;
v:array[1..100000] of longint;
f1,f2:text;
procedure dfs(l:longint);
var i:longint;
begin
v[l]:=1;
for i:=1 to n do
if (a[l,i]=1) and (v[i]=0) then dfs(i);
end;
begin
assign(f1,'dfs.in');
reset(f1);
readln(f1,n,m);
for i:=1 to m do begin
readln(f1,k,l);
a[k,l]:=1;
a[l,k]:=1;
end;
close(f1);
for i:=1 to n do dfs(i);
k:=0;
for i:=1 to n do if v[i]=1 then Inc(k);
assign(f2,'dfs.out');
rewrite(f2);
writeln(f2,k div 2);
end.