const inf=maxlongint div 5;
var f,g:text;
a,b:array[1..1024] of longint;
sum:array[0..200000] of longint;
n,i,j,k,l,m,s,max,min:longint;


begin
assign(f,'energii.in');
assign(g,'energii.out');
reset(F);
rewrite(G);
readln(f,n);
readln(f,s);
max:=0;
for i:=1 to n do
        begin
        readln(f,a[i],b[i]);
        if a[i]>max then max:=a[i];
        end;

for i:=1 to s+max do sum[i]:=inf;sum[0]:=0;
for i:=1 to n do
        for j:=s+a[i]-1 downto a[i] do
                if (sum[j-a[i]]+b[i]<sum[j]) then
                        sum[j]:=sum[j-a[i]]+b[i];
min:=maxlongint;
for i:=s to s+max do
        if sum[i]<min then min:=sum[i];
if min<inf then writeln(g,min)
else writeln(g,-1);
close(F);
close(G);
end.