import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    static final long MAX = 1000000000000000000L;
    static long[][] dp;
    static long p;
    static boolean[] isDouble;
    static int[] values;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        p = sc.nextLong();
        int k = sc.nextInt();
        isDouble = new boolean[n];
        values = new int[n];
        for (int i = 0; i < n; i++) {
            isDouble[i] = sc.nextInt() == 2;
            values[i] = sc.nextInt();
        }
        dp = new long[n][k + 1];
        for (long[] arr : dp) {
            Arrays.fill(arr, Long.MIN_VALUE);
        }
        long ans = dfw(n - 1, k);
        System.out.println(ans > MAX ? -1 : ans);
    }
    
    static long dfw(int idx, int v) {
        if (idx + 1 < v) {
            return Long.MIN_VALUE / 2;
        }
        if (v == 0) {
            return p;
        }
        if (dp[idx][v] == Long.MIN_VALUE) {
            dp[idx][v] = Math.max(dfw(idx - 1, v), func(isDouble[idx], values[idx], dfw(idx - 1, v - 1)));
        }
        return dp[idx][v];
    }
    
    static long func(boolean isD, int v, long current) {
        if (isD) {
            return Math.min(MAX + 1, current * 2);
        } else {
            return Math.min(MAX + 1, current + v);
        }
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}