program la_pescuit;
{$M 65000,0,655350}
type date=record
	        p,t:word;
          end;
     vector=array[1..16000]of date;
var n,k,tt,i,y:word;
    v:vector;
    f,g:text;
    max,s:longint;

procedure sortare;
var aux,aux1,j:word;
begin
for i:=2 to n do
	begin
  aux:=v[i].p;
  aux1:=v[i].t;
  j:=i-1;
  while(j>0) and (aux>v[j].p) do
  	begin
    v[j+1].p:=v[j].p;
    v[j+1].t:=v[j].t;
    j:=j-1;
    end;
   v[j+1].p:=aux;
   v[j+1].t:=aux1;
 end;
end;


{
procedure comb(x:word);
begin
if x=k then
  begin
  	if max<s then
  		max:=s;
  end
else
  begin
  x:=x+1;
  for i:=x to (n-k+x) do
    begin
    s:=s+v[i].p;
	  comb(x);
		end;
  end;
s:=0;
end;              }

begin
assign(f,'peste.in');
reset(f);
assign(g,'peste.out');
rewrite(g);
read(f,n,k,tt);
for i:=1 to n do
readln(f,v[i].p,v[i].t);
sortare;
s:=0;
for i:=1 to k do
 s:=s+v[i].p;
write(g,s);
close(f);
close(g);
end.