TWINS Pascal

var
   p:array[1..maxx] of byte;
procedure sang(n:longint);
var i,j:longint;
begin
    for i:=1 to n do p[i]:=0;
    p[1]:=1;
    for i:=2 to trunc(sqrt(n)) do
        if p[i]=0 then
        begin
            j:=i*i;
            while j<=n do
            begin
                p[j]:=1;
                j:=j+i;
             end;
        end;
end;

procedure solve;
var n,k,d,i:longint;
begin
    d:=0;
    read(n,k);sang(n);
    for i:=1 to n-k do
        if (p[i]=0) and (p[i+k]=0) then inc(d);
    write(d);
end;

begin
    assign(input,fin);reset(input);
    assign(output,fon);rewrite(output);
    solve;
    close(input);close(output);
end.