package _1163;
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.UncheckedIOException;
import java.lang.reflect.Array;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Main {
    public void exec() {
        int n = stdin.nextInt();
        long x = stdin.nextLong();
        long[] a = stdin.nextLongArray(n);
        long[] b = stdin.nextLongArray(n);

        for (int i = 0; i < n; i++) {
            a[i] -= x;
        }

        if (Arrays.stream(a).sum() >= 0) {
            stdout.println(0);
            return;
        }

        if (Arrays.stream(a).allMatch(v -> v < 0)) {
            stdout.println(-1);
            return;
        }

        List<Map<Long, Long>> dp = IntStream.range(0, n+1).mapToObj(unused -> new HashMap<Long, Long>()).collect(Collectors.toList());
//        dp.get(0).put(0L, 0L);
        for (int i = 0; i < n; i++) {
            for (long k : dp.get(i).keySet()) {
                dp.get(i+1).put(k, Math.min(dp.get(i+1).getOrDefault(k, Long.MAX_VALUE), dp.get(i).get(k)));
                dp.get(i+1).put(k+a[i], Math.min(dp.get(i+1).getOrDefault(k+a[i], Long.MAX_VALUE), dp.get(i).get(k)+b[i]));
            }
            dp.get(i+1).put(a[i], Math.min(dp.get(i+1).getOrDefault(a[i], Long.MAX_VALUE), b[i]));
        }

        long ans = dp.get(n).entrySet().stream().filter(e -> e.getKey() >= 0).mapToLong(Entry::getValue).min().getAsLong();
        stdout.println(ans);
    }

    private static final Stdin stdin = new Stdin();
    private static final Stdout stdout = new Stdout();

    public static void main(String[] args) {
        try {
            new Main().exec();
        } finally {
            stdout.flush();
        }
    }

    public static class Stdin {
        private BufferedReader stdin;
        private Deque<String> tokens;
        private Pattern delim;

        public Stdin() {
            stdin = new BufferedReader(new InputStreamReader(System.in));
            tokens = new ArrayDeque<>();
            delim = Pattern.compile(" ");
        }

        public String nextString() {
            try {
                if (tokens.isEmpty()) {
                    String line = stdin.readLine();
                    if (line == null) {
                        throw new UncheckedIOException(new EOFException());
                    }
                    delim.splitAsStream(line).forEach(tokens::addLast);
                }
                return tokens.pollFirst();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        }

        public int nextInt() {
            return Integer.parseInt(nextString());
        }

        public double nextDouble() {
            return Double.parseDouble(nextString());
        }

        public long nextLong() {
            return Long.parseLong(nextString());
        }

        public String[] nextStringArray(int n) {
            String[] a = new String[n];
            for (int i = 0; i < n; i++) a[i] = nextString();
            return a;
        }

        public int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }

        public double[] nextDoubleArray(int n) {
            double[] a = new double[n];
            for (int i = 0; i < n; i++) a[i] = nextDouble();
            return a;
        }

        public long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++) a[i] = nextLong();
            return a;
        }
    }

    public static class Stdout {
        private PrintWriter stdout;

        public Stdout() {
            stdout =  new PrintWriter(System.out, false);
        }

        public void printf(String format, Object ... args) {
            String line = String.format(format, args);
            if (line.endsWith(System.lineSeparator())) {
                stdout.print(line);
            } else {
                stdout.println(line);
            }
        }

        public void println(Object ... objs) {
            String line = Arrays.stream(objs).map(Objects::toString).collect(Collectors.joining(" "));
            stdout.println(line);
        }

        public void debug(Object ... objs) {
            String line = Arrays.stream(objs).map(this::deepToString).collect(Collectors.joining(" "));
            stdout.printf("DEBUG: %s%n", line);
        }

        private String deepToString(Object o) {
            if (o == null) {
                return "null";
            }

            // 配列の場合
            if (o.getClass().isArray()) {
                int len = Array.getLength(o);
                String[] tokens = new String[len];
                for (int i = 0; i < len; i++) {
                    tokens[i] = deepToString(Array.get(o, i));
                }
                return "{" + String.join(",", tokens) + "}";
            }

            return Objects.toString(o);
        }

        private void flush() {
            stdout.flush();
        }
    }
}