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

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var m = int.Parse(line[1]);
        var x = int.Parse(line[2]);
        var d = new Dictionary<int, List<int>>();
        for (int i = 0; i < n; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            var a = int.Parse(line[0]);
            var b = int.Parse(line[1]);
            if (!d.ContainsKey(b)) d[b] = new List<int>();
            d[b].Add(a);
        }
        var s = new long[n];
        var p = 0;
        foreach (var y in d)
        {
            var first = true;
            foreach (var z in y.Value.OrderByDescending(z => z))
            {
                if (first) { s[p++] = z + x; first = false; }
                else s[p++] = z;
            }
        }
        Array.Sort(s);
        Array.Reverse(s);
        var t = new long[n + 1];
        for (int i = 1; i <= n; i++) t[i] = t[i - 1] + s[i - 1];
        Console.ReadLine();
        line = Console.ReadLine().Trim().Split(' ');
        var c = Array.ConvertAll(line, int.Parse);
        var ans = 0L;
        foreach (var y in c) ans += t[y];
        Console.WriteLine(ans);
    }
}