/CDIE - Cắm điện

              USES CRT;
        type    Arr=array[0..1000000] of longint;
        var     n,m,i,res:longint;
                a:Arr;
PROCEDURE SORT (var a:Arr; l,r:longint);
var i,j,x,tg:longint;
begin
    i:=l;
    j:=r;
    x:=a[(l+r) div 2];
    repeat
        while a[i]>x do inc(i);
        while a[j]<x do dec(j);
        if not (i>j) then begin
            tg:=a[i];
            a[i]:=a[j];
            a[j]:=tg;
            inc(i);
            dec(j);
        end;
    until i>j;
    if l<j then SORT(a,l,j);
    if i<r then SORT(a,i,r);
end;
                begin
                    readln(n,m);
                    for i:=1 to n do read(a[i]);
                    SORT(a,1,n);
                    res:=1; i:=0;
                    for i:=1 to n+1 do begin
                        if res>=m then break;
                        res:=res+a[i]-1;
                    end;
                    if i<=n then writeln(i-1) else writeln(-1);
                    readln;

                end.