using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        Solve();
        Console.Out.Flush();
    }
    static void Solve()
    {
        var N = sc.ReadInt();
        var M = sc.ReadInt();
        var AB = sc.ReadTupArray(N);
        AB = AB.OrderBy(ab => ab.Item1).ToArray();
        var ans = 0L;
        var pq = new PriorityQueue<int>();
        var index = 0;
        for (int i = M - 1; i >= 0; i--)
        {
            var rem = (M - 1) - i + 1;
            while (index < N && AB[index].Item1 == rem)
            {
                pq.Enqueue(AB[index].Item2);
                index++;
            }
            if (pq.Count > 0)
            {
                ans += pq.Dequeue();
            }
        }
        Console.WriteLine(ans);
    }
    // Comparison<T> f = (x, y) => x.CompareTo(y);
    // Comparer<T>.Create(f)
    class PriorityQueue<T>
    {
        public int Count;
        private int Capacity;
        private bool IsMaxHeap;
        private T[] Buffer;
        private IComparer<T> Cmp;
        public PriorityQueue(bool isMaxHeap = true, IComparer<T> cmp = null)
        {
            Count = 0;
            Capacity = 1 << 10;
            IsMaxHeap = isMaxHeap;
            Buffer = new T[Capacity];
            if (cmp != null) Cmp = cmp;
            else Cmp = Comparer<T>.Default;
        }
        public PriorityQueue(int capacity, bool isMaxHeap = true, IComparer<T> cmp = null)
        {
            Count = 0;
            Capacity = Math.Max(16, capacity);
            IsMaxHeap = isMaxHeap;
            Buffer = new T[Capacity];
            if (cmp != null) Cmp = cmp;
            else Cmp = Comparer<T>.Default;
        }
        private void Resize()
        {
            Capacity <<= 1;
            Array.Resize(ref Buffer, Capacity);
        }
        public void Enqueue(T value)
        {
            if (Count == Capacity) Resize();
            Buffer[Count] = value;
            Count++;
            UpHeap();
        }
        public T Dequeue()
        {
            var res = Buffer[0];
            Swap(0, Count - 1);
            Count--;
            DownHeap();
            return res;
        }
        public T Peek() { return Buffer[0]; }
        private void Swap(int i, int j)
        {
            var tmp = Buffer[i];
            Buffer[i] = Buffer[j];
            Buffer[j] = tmp;
        }
        private void UpHeap()
        {
            var n = this.Count - 1;
            while (n != 0)
            {
                var parent = (n - 1) / 2;
                if (Compare(Buffer[n], Buffer[parent]) > 0)
                {
                    Swap(n, parent);
                    n = parent;
                }
                else break;
            }
        }
        private void DownHeap()
        {
            var parent = 0;
            while (true)
            {
                var child = 2 * parent + 1;
                if (child > this.Count - 1) break;
                if (child < Count - 1 && Compare(Buffer[child], Buffer[child + 1]) < 0)
                {
                    child += 1;
                }
                if (Compare(Buffer[parent], Buffer[child]) < 0)
                {
                    Swap(parent, child);
                    parent = child;
                }
                else break;
            }
        }
        private int Compare(T x, T y)
        {
            var res = Cmp.Compare(x, y);
            if (!IsMaxHeap) res *= -1;
            return res;
        }
    }
    static Scanner sc = new Scanner();
}
class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public Tuple<int, int> ReadTup(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<long, long> ReadTupLong(int add = 0)
    {
        return Tuple.Create(this.ReadLong() + add, this.ReadLong() + add);
    }
    public Tuple<int, int, int> ReadTup3(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<int, int, int, int> ReadTup4(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
    public Tuple<long, long>[] ReadTupLongArray(int n, int add = 0)
    {
        var array = new Tuple<long, long>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTupLong(add);
        }
        return array;
    }
    public Tuple<int, int>[] ReadTupArray(int n, int add = 0)
    {
        var array = new Tuple<int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup(add);
        }
        return array;
    }
    public Tuple<int, int, int>[] ReadTup3Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup3(add);
        }
        return array;
    }
    public Tuple<int, int, int, int>[] ReadTup4Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup4(add);
        }
        return array;
    }
}


Measured memory_bytes: 26696