type sir=array[1..10001] of integer;
var f,g:text;
    g,w,i,j:integer;
    eg,cg:sir;
    ef:array[1..10001] of real;
    aux:real;

begin
assign(f,'energii.in');reset(f);
assign(g,'energii.out');rewrite(g);
read(f,g,w);
for i:=1 to g do begin
read(f,eg[i],cg[i]);
ef[i]:=eg[i]/cg[i];
end;
for i:=1 to g-1 do
    for j:=i+1 to g do
    if ef[i]<ef[j] then begin aux:=ef[i];
                              ef[i]:=ef[j];
                              ef[j]:=aux;
                              aux:=eg[i];
                              eg[i]:=eg[j];
                              eg[j]:=aux;
                              aux:=cg[i];
                              cg[i]:=cg[j];
                              cg[j]:=aux;
                              end;
s:=eg[1];
c:=cg[1];
i:=2;
while (s<w) and (i<=g) do begin
s:=s+eg[i];
c:=c+cg[i];
inc(i)
end;

if s>=w then write(g,c)
        else write(g,'-1');
close(g);
end.