const
    MAX_K = 10101010;

var
    a: array[0..MAX_K] of integer;
    f: text;

begin
    Assign(f, '27-124b.txt');
    reset(f);

    var N, K, V, M: integer;
    readln(f, N, K, V, M);
    M += 1;

    for var i := 0 to K - 1 do
        a[i] := 0;

    var sum: int64 = 0;

    for var i := 1 to N do
    begin
        var id, cnt: integer;
        readln(f, id, cnt);
        id := id mod K;
        var x := (cnt + V - 1) div V;
        a[id] := x;
        if (id < M) or (id > K - M) then
            sum += x;
    end;

    if M > K - M then
        writeln(sum)
    else
    begin
        var ans: int64 = 0;
        for var i := 0 to K - 1 do
        begin
            if a[i] <> 0 then
                ans := max(ans, sum);
            sum += a[(i + M) mod K];
            sum -= a[(K + i - M) mod K];
        end;
        writeln(ans);
    end;

end.