program energii;
type generator=record
        e,c:longint;
end;
var f,g:text;
        n,w:longint;
        v:array[1..10000] of generator;



procedure iofile;
var i:longint;
begin
        assign(f,'energii.in');
        reset(f);
        assign(g,'energii.out');
        rewrite(g);
        readln(f,n);
        readln(f,w);
        for i:=1 to n do
                readln(f,v[i].e,v[i].c);
        close(f);
end;


procedure pozitie(var m:longint;p,u:longint);
var i,j,di,dj,aux:longint;
        aux1:generator;
begin
        i:=p;
        j:=u;
        di:=0;
        dj:=-1;
        while i<j do
                begin
                        if v[i].e/v[i].c<v[j].e/v[j].c then
                                begin
                                        aux:=di;
                                        di:=-dj;
                                        dj:=-aux;
                                        aux1:=v[i];
                                        v[i]:=v[j];
                                        v[j]:=aux1;
                                end;
                        i:=i+di;
                        j:=j+dj;
                end;
        m:=i;
end;


procedure quick(p,u:longint);
var m:longint;
begin
        if p<u then
                begin
                        pozitie(m,p,u);
                        quick(p,m-1);
                        quick(m+1,u);
                end;
end;



procedure prel;
var i,poz,sum,sc:longint;
begin
        quick(1,n);
        poz:=1;
        sum:=0;
        sc:=0;
        while (poz<=n)and(sum<w) do
                begin
                     sum:=sum+v[poz].e;
                     sc:=sc+v[poz].c;
                     inc(poz);
                end;
        if sum<w then
                begin
                        writeln(g,'-1');
                        close(g);
                        halt;
                end;
        poz:=1;
        while sum-v[poz].e>=w do
                begin
                        sum:=sum-v[poz].e;
                        sc:=sc-v[poz].c;
                        inc(poz);
                end;
        writeln(g,sc);
        close(g);
end;


begin
        iofile;
        prel;
end.