#nullable enable

using System.Numerics;

void Run()
{
    var n = Int();
    var m = Int();
    var a0 = 0;
    var cards = new List<(int, int)>();
    for (var i = 0; i < n; i++)
    {
        var c = Int();
        var d = Int();
        if (c == 0)
        {
            a0 += d;
        }
        else
        {
            cards.Add((c, d));
        }
    }
    n = cards.Count;
    cards.Sort();
    cards.Reverse();
    var tz = new int[13];
    tz[0] = 1;
    for (var i = 1; i <= 12; i++) tz[i] = tz[i - 1] * 2;
    var min = long.MinValue / 8;
    var f = new long[m + 1, n + 1, 13];
    for (var i = 0; i <= m; i++) for (var j = 0; j <= n; j++) for (var k = 0; k <= 12; k++) f[i, j, k] = min;
    f[m, 0, 0] = 0;
    var ans = 0L;
    for (var y = 0; y < n; y++)
    {
        var (c, d) = cards[y];
        for (var x = 0; x <= m; x++) for (var z = 0; z <= 12; z++)
        {
            var v = f[x, y, z];
            f[x, y + 1, z] = Math.Max(f[x, y + 1, z], v);
            var nx = x - c * tz[z];
            if (nx >= 0) f[nx, y + 1, z + 1] = Math.Max(f[nx, y + 1, z + 1], v + d);
        }
    }
    for (var x = 0; x <= m; x++) for (var z = 0; z <= 12; z++) ans = Math.Max(ans, f[x, n, z]);
    Out(ans + a0);
}

#region
AtCoderIO _io_;
var _backend_ = new StandardIOBackend();
_io_ = new(){ Backend = _backend_ };
Run();
_backend_.Flush();

string String() => _io_.Next();
int Int() => int.Parse(String());
void Out(object? x, string? sep = null) => _io_.Out(x, sep);

class AtCoderIO
{
    public required StandardIOBackend Backend { get; init; }

    Memory<string> _input = Array.Empty<string>();
    int _iter = 0;
    public string Next()
    {
        while (_iter >= _input.Length) (_input, _iter) = (Backend.ReadLine().Split(' '), 0);
        return _input.Span[_iter++];
    }

    public void Out(object? x, string? separator = null)
    {
        if (x == null) return;
        separator ??= Environment.NewLine;
        if (x is System.Collections.IEnumerable a and not string)
        {
            var objects = a.Cast<object>();
            if (separator == Environment.NewLine && !objects.Any()) return;
            x = string.Join(separator, objects);
        }
        Backend.WriteLine(x);
    }
}

class StandardIOBackend
{
    readonly StreamReader _sr = new(Console.OpenStandardInput());
    readonly StreamWriter _sw = new(Console.OpenStandardOutput()) { AutoFlush = false };
    public string ReadLine() => _sr.ReadLine()!;
    public void WriteLine(object? value) => _sw.WriteLine(value);
    public void Flush() => _sw.Flush();
}
#endregion

static class Extensions
{
    public static T[] Repeat<T>(this int time, Func<T> F) => Enumerable.Range(0, time).Select(_ => F()).ToArray();
}