var rel:array[1..10000,1..10000] of boolean;
    f,g:text;
    util:array[1..10000] of boolean;
    dr,st:array[1..10000] of longint;
    m,x,y,i,nr,n1,n2:longint;

function cupleaza(nod:longint):boolean;
 var i:longint;
 begin
  if util[nod] then cupleaza:=false
  else begin
   util[nod]:=true; cupleaza:=false;
   for i:=1 to n2 do
    if rel[nod,i] then
     if (dr[i]=0) or (cupleaza(dr[i])) then begin
      st[nod]:=i; dr[i]:=nod;
      cupleaza:=true;
      break;
     end;
  end;
 end;

begin
 assign(f,'cuplaj.in'); reset(f);
 assign(g,'cuplaj.out'); rewrite(g);
 read(f,n1,n2,m);
 for i:=1 to m do begin
  read(f,x,y);
  rel[x,y]:=true;
 end;
 nr:=0;
 for i:=1 to n1 do
  if st[i]=0 then begin
   if cupleaza(i) then inc(nr)
   else begin
    fillchar(util,sizeof(util),false);
    if cupleaza(i) then
     inc(nr);
   end;
  end;
 writeln(g,nr);
 for i:=1 to n1 do
  if st[i]<>0 then
   writeln(g,i,' ',st[i]);
 close(f); close(g);
end.