program energii;
type
tabel=array [0..5001] of longint;
var
t,tt:tabel;
n,m,i,j,k,l,v,vv:longint;
f1,f2:text;
function min(a,b:longint):longint;
begin
if a>b then min:=b else
min:=a;
end;
begin
assign (f1,'energii.in');
assign (f2,'energii.out');
reset (f1);
rewrite (f2);
readln (f1,n);
readln (f1,m);
for i:=1 to m do
t[i]:=1000000000;
for i:=1 to n do begin
readln (f1,v,vv);
for j:=1 to m do
if v>=j then tt[j]:=min(vv,t[j]) else
tt[j]:=min(tt[j],tt[j-v]+vv);
end;
if tt[m]=1000000000 then writeln (f2,-1) else
writeln (f2,tt[m]);
close (f1);
close (f2);
end.