import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;

/**
 * Gluttony
 */
public class Main {

    public static void main(String[] args) throws Exception {
        try (Reader r = new Reader(System.in)) {
            int N = r.i();
            long K = r.l();

            long[] A = r.la();
            long[] F = r.la();

            long sum = Arrays.stream(A).sum();
            if (sum <= K) {
                System.out.println(0);
                return;
            }

            Arrays.sort(A);
            Arrays.sort(F);

            long min = 0;
            long max = 0;
            for (int i = 0; i < N; i++) {
                max = Math.max(max, A[i] * F[N - 1 - i]);
            }

            while (max - min > 1) {
                long mid = (min + max) / 2;

                long need = 0;
                for (int i = 0; i < N; i++) {
                    need += Math.max(0, A[i] - mid / F[N - 1 - i]);
                }

                if (need > K) {
                    min = mid;
                } else {
                    max = mid;
                }
            }

            System.out.println(max);
        }

    }

    public static class Reader implements AutoCloseable {

        private BufferedReader br;

        private String[] buf;

        private int bufidx = -1;

        public Reader(InputStream in) {
            this.br = new BufferedReader(new InputStreamReader(in));
        }

        @Override
        public void close() throws Exception {
            br.close();
        }

        private void readBuf() throws IOException {
            if (bufidx == -1 || bufidx == buf.length) {
                buf = br.readLine().split(" ");
                bufidx = 0;
            }
        }

        public String s() throws IOException {
            readBuf();
            return buf[bufidx++];
        }

        public int i() throws IOException {
            return Integer.parseInt(s());
        }

        public long l() throws IOException {
            return Long.parseLong(s());
        }

        public double d() throws IOException {
            return Double.parseDouble(s());
        }

        public String[] sa() throws IOException {
            readBuf();
            if (bufidx != 0) {
                throw new RuntimeException("illegal read");
            }
            bufidx = -1;
            return buf;
        }

        public int[] ia() throws IOException {
            String[] sa = sa();
            int[] ia = new int[sa.length];
            for (int i = 0; i < sa.length; i++) {
                ia[i] = Integer.parseInt(sa[i]);
            }
            return ia;
        }

        public long[] la() throws IOException {
            String[] sa = sa();
            long[] la = new long[sa.length];
            for (int i = 0; i < sa.length; i++) {
                la[i] = Long.parseLong(sa[i]);
            }
            return la;
        }

        public double[] da() throws IOException {
            String[] sa = sa();
            double[] da = new double[sa.length];
            for (int i = 0; i < sa.length; i++) {
                da[i] = Double.parseDouble(sa[i]);
            }
            return da;
        }

        public int[][] im(int N) throws IOException {
            int[][] im = new int[N][];
            for (int i = 0; i < N; i++) {
                im[i] = ia();
            }
            return im;
        }

        public long[][] lm(int N) throws IOException {
            long[][] lm = new long[N][];
            for (int i = 0; i < N; i++) {
                lm[i] = la();
            }
            return lm;
        }

        public double[][] dm(int N) throws IOException {
            double[][] dm = new double[N][];
            for (int i = 0; i < N; i++) {
                dm[i] = da();
            }
            return dm;
        }

    }

}


Measured memory_bytes: 72608