using System;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using static System.Math;
using Debug = System.Diagnostics.Debug;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;

static class P
{
    static void Main()
    {
        var n = NextInt;
        var m = NextInt;
        List<int>[] jobs = Enumerable.Repeat(0, 100001).Select(_ => new List<int>()).ToArray();
        for (int i = 0; i < n; i++)
        {
            jobs[NextInt - 1].Add(NextInt);
        }
        int reward = 0;
        PriorityQueue<int> pq = new PriorityQueue<int>(true);
        for (int i = 0; i < m; i++)
        {
            foreach (var job in jobs[i])
                pq.Push(job);
            if (pq.Count != 0) reward += pq.Pop();
        }
        Console.WriteLine(reward);
    }

    static readonly TextReader In = Console.In;
    static int NextInt
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        get
        {
            int res = 0;
            int next = In.Read();
            int rev = 1;
            while (45 > next || next > 57) next = In.Read();
            if (next == 45) { next = In.Read(); rev = -1; }
            while (48 <= next && next <= 57)
            {
                res = res * 10 + next - 48;
                next = In.Read();
            }
            return res * rev;
        }
    }
}


class PriorityQueue<T> where T : IComparable<T>
{
    public int Count { get; private set; }
    private bool Descendance;
    private T[] data = new T[65536];
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public PriorityQueue(bool descendance = false) { Descendance = descendance; }
    public T Top
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        get { ValidateNonEmpty(); return data[1]; }
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public T Pop()
    {
        var top = Top;
        var elem = data[Count--];
        int index = 1;
        while (true)
        {
            if ((index << 1) >= Count)
            {
                if (index << 1 > Count) break;
                if (elem.CompareTo(data[index << 1]) > 0 ^ Descendance) data[index] = data[index <<= 1];
                else break;
            }
            else
            {
                var nextIndex = data[index << 1].CompareTo(data[(index << 1) + 1]) <= 0 ^ Descendance ? (index << 1) : (index << 1) + 1;
                if (elem.CompareTo(data[nextIndex]) > 0 ^ Descendance) data[index] = data[index = nextIndex];
                else break;
            }
        }
        data[index] = elem;
        return top;
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public void Push(T value)
    {
        int index = ++Count;
        if (data.Length == Count) Extend(data.Length * 2);
        while ((index >> 1) != 0)
        {
            if (data[index >> 1].CompareTo(value) > 0 ^ Descendance) data[index] = data[index >>= 1];
            else break;
        }
        data[index] = value;
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private void Extend(int newSize)
    {
        T[] newDatas = new T[newSize];
        data.CopyTo(newDatas, 0);
        data = newDatas;
    }
    private void ValidateNonEmpty() { if (Count == 0) throw new Exception(); }
}

Measured memory_bytes: 24484