{
 haoi2009 moni2 t3
 rp++
 time:2009.4.21
}
program cch(input,output);
var
 hang,lie:array[1..200000] of longint;
 x,y:array[1..600000] of longint;
 n,m:longint;

procedure init;
var
 i:longint;
begin
 assign(input,'board.in');
 assign(output,'board.out');
 reset(input);
 rewrite(output);
 readln(n,m);
 for i:=1 to m do
  readln(x[i],y[i]);
end;

function min(x,y:longint):longint;
begin
 if x<y then exit(x)
  else exit(y);
end;

procedure main;
var
 i,h,l,ans1,ans,tmp1,tmp2:longint;
begin
 for i:=1 to n do
  hang[i]:=0;
 for i:=1 to n do
  lie[i]:=0;
 for i:=1 to m do
  begin
   inc(hang[x[i]]); inc(lie[y[i]]);
  end;
 h:=0; l:=0;
 for i:=1 to n do
  if hang[i]>0 then inc(h);
 for i:=1 to n do
  if lie[i]>0 then inc(l);
 ans1:=min(h,l);
 ans:=0;
 for i:=1 to m do
  begin
   dec(hang[x[i]]); dec(lie[y[i]]);
   tmp1:=h; tmp2:=l;
   if hang[x[i]]=0 then dec(h);
   if hang[y[i]]=0 then dec(l);
   if ans1=min(h,l) then inc(ans);
   inc(hang[x[i]]); inc(lie[y[i]]);
   h:=tmp1; l:=tmp2;
  end;
 writeln(ans);
 close(input);
 close(output);
end;

begin
 init;
 main;
end.