using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var p = long.Parse(line[1]);
        var k = int.Parse(line[2]);
        var a = new int[n];
        for (int i = 0; i < n; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            if (line[0] == "1") a[i] = int.Parse(line[1]);
        }
        getAns(n, p, k, a);
    }
    static void getAns(int n, long p, int k, int[] a)
    {
        var MAX = (long)1e18;
        var HALF = MAX / 2;
        var dp = new long[n + 1, k + 1];
        dp[0, 0] = p;
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j <= k; j++)
            {
                if (dp[i, j] > 0)
                {
                    dp[i + 1, j] = Max(dp[i + 1, j], dp[i, j]);
                    if (j == k) continue;
                    if (a[i] > 0)
                    {
                        dp[i + 1, j + 1] = Max(dp[i + 1, j + 1], dp[i, j] + a[i]);
                        if (dp[i + 1, j + 1] > MAX) { Console.WriteLine(-1); return; }
                    }
                    else
                    {
                        if (dp[i, j] > HALF) { Console.WriteLine(-1); return; }
                        dp[i + 1, j + 1] = Max(dp[i + 1, j + 1], dp[i, j] * 2);
                    }
                }
            }
        }
        Console.WriteLine(dp[n, k]);
    }
}