var i,j,n,p,min,s:longint;
    v,x,y:array[0..20000]of longint;

begin
assign(input,'energii.in');reset(input);
assign(output,'energii.out');rewrite(output);
readln(n,p);
for i:=1 to n do
        begin
        readln(v[i],x[i]);
        s:=s+v[i];
        end;
y[0]:=0;
for i:=1 to 20000 do
        y[i]:=maxlongint;

for i:=1 to n do
        for j:=p downto 0 do
                if y[j]<>maxlongint then
                        begin
                        if y[j]+x[i]<y[j+v[i]] then
                                y[j+v[i]]:=y[j]+x[i];
                        end;
min:=maxlongint;
for i:=p to 20000 do
        if y[i]<min then
                min:=y[i];
if min=maxlongint then
        min:=-1;
writeln(min);
close(input);close(output);
end.