import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.function.Function;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.util.Comparator;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author anand.oza
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        EGluttony solver = new EGluttony();
        solver.solve(1, in, out);
        out.close();
    }

    static class EGluttony {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            long k = in.nextLong();
            Long[] a = in.readLongObjectArray(n);
            Long[] f = in.readLongObjectArray(n);

            Arrays.sort(a);
            Arrays.sort(f, Comparator.reverseOrder());

            long answer = BinarySearch.binarySearchLong(score -> {
                long cost = 0;

                for (int i = 0; i < n; i++) {
                    if (a[i] * f[i] > score) {
                        long extra = a[i] * f[i] - score;
                        cost += (extra + f[i] - 1) / f[i];
                    }
                }

                return cost <= k;
            });

            out.println(answer);
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

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

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

        public Long[] readLongObjectArray(int n) {
            Long[] x = new Long[n];
            for (int i = 0; i < n; i++) {
                x[i] = nextLong();
            }
            return x;
        }

    }

    static class BinarySearch {
        public static long binarySearchLong(Function<Long, Boolean> bigEnough) {
            long tooSmall = 0, tooBig;
            if (bigEnough.apply(tooSmall)) {
                return tooSmall;
            }

            for (tooBig = 1; !bigEnough.apply(tooBig); tooBig *= 2)
                ;

            if (!bigEnough.apply(tooBig - 1)) {
                return tooBig;
            }

            while (tooBig - tooSmall > 1) {
                long center = tooSmall + (tooBig - tooSmall) / 2;
                if (!bigEnough.apply(center)) {
                    tooSmall = center;
                } else {
                    tooBig = center;
                }
            }

            return tooBig;
        }

    }
}



Measured memory_bytes: 66820