var head,vet,next,len1,len2,x,y,p1,p2,dis,a,b,fan:array[..]of longint;

     pre:array[..,..]of longint;

     inq:array[..]of boolean;

     q:array[..]of longint;

     n,m,i,j,ans,tot,source,src,s,t1,t2:longint;

 function min(x,y:longint):longint;

 begin

  if x<y then exit(x);

  exit(y);

 end;

 procedure add(a,b,c,d:longint);

 begin

  inc(tot);

  next[tot]:=head[a];

  vet[tot]:=b;

  len1[tot]:=c;

  len2[tot]:=d;

  head[a]:=tot;

  inc(tot);

  next[tot]:=head[b];

  vet[tot]:=a;

  len1[tot]:=;

  len2[tot]:=-d;

  head[b]:=tot;

 end;

 function find(x,y:longint):boolean;

 var i:longint;

 begin

  for i:= to n do

   if (x=a[i])and(y=b[i]) then exit(true);

  exit(false);

 end;

 function spfa:boolean;

 var u,e,v,i,t,w,t1,w1:longint;

 begin

  for i:= to s do

  begin

   dis[i]:=maxlongint>>;

   inq[i]:=false;

  end;

  t:=; w:=; t1:=; w1:=; q[]:=source; dis[source]:=; inq[source]:=true;

  while t<w do

  begin

   inc(t); inc(t1);

   if t1= then t1:=;

   u:=q[t1]; inq[u]:=false;

   e:=head[u];

   while e<> do

   begin

    v:=vet[e];

    if (len1[e]>)and(dis[u]+len2[e]<dis[v]) then

    begin

     pre[v,]:=u;

     pre[v,]:=e;

     dis[v]:=dis[u]+len2[e];

     if not inq[v] then

     begin

      inc(w); inc(w1);

      if w1= then w1:=;

      q[w1]:=v; inq[v]:=true;

     end;

    end;

    e:=next[e];

   end;

  end;

  if dis[src]=maxlongint>> then exit(false);

  exit(true);

 end;

 procedure mcf;

 var k,e,t:longint;

 begin

  k:=src; t:=maxlongint;

  while k<>source do

  begin

   t:=min(t,len1[pre[k,]]);

   k:=pre[k,];

  end;

  k:=src;

  while k<>source do

  begin

   e:=pre[k,];

   len1[e]:=len1[e]-t;

   len1[fan[e]]:=len1[fan[e]]+t;

   ans:=ans+t*len2[e];

   k:=pre[k,];

  end;

 end;

 begin

  assign(input,'guess.in'); reset(input);

  assign(output,'guess.out'); rewrite(output);

  readln(n);

  for i:= to  do

   if i and = then fan[i]:=i+

    else fan[i]:=i-;

  for i:= to n do

  begin

   readln(a[i],b[i]);

   inc(x[a[i]]); inc(y[b[i]]);

  end;

  for i:= to  do

   if x[i]> then inc(s);

  for i:= to  do

   if y[i]> then inc(s);

  source:=s+; src:=s+; s:=s+;

  for i:= to  do

   if x[i]> then

   begin

    inc(t1); p1[t1]:=i;

    add(source,t1,x[i],);

   end;

  for i:= to  do

   if y[i]> then

   begin

    inc(t2); p2[t2]:=i;

    add(t1+t2,src,y[i],);

   end;

  for i:= to t1 do

   for j:= to t2 do

    if find(p1[i],p2[j]) then add(i,j+t1,,)

     else add(i,j+t1,,);

  while spfa do mcf;

  writeln(ans);

  close(input);

  close(output);

 end.