import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;

class Main {
    public static void main(String[] args) throws IOException {
        try (PrintWriter writer = new PrintWriter(System.out); InputReader reader = new InputReader(System.in)) {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        }
    }
}

class InputReader implements Closeable, AutoCloseable {
    private final BufferedReader br;

    InputReader(InputStream inputStream) {
        this.br = new BufferedReader(new InputStreamReader(inputStream));
    }

    String readLine() throws IOException {
        return this.br.readLine();
    }

    int readInt() throws IOException {
        return Integer.parseInt(this.readLine());
    }

    long readLong() throws IOException {
        return Long.parseLong(this.readLine());
    }

    String[] readStringsSplitByDelimiter(String delimiter) throws IOException {
        return this.readLine().split(delimiter);
    }

    int[] readIntsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        int[] ints = new int[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            ints[i] = Integer.parseInt(strings[i]);
        }

        return ints;
    }

    long[] readLongsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        long[] longs = new long[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            longs[i] = Long.parseLong(strings[i]);
        }

        return longs;
    }

    @Override
    public void close() throws IOException {
        this.br.close();
    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.Closeable; Closeable java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.PrintWriter; PrintWriter java.io class Main {
    public static void main(String[] args) throws IOException {
        try (PrintWriter writer = new PrintWriter(System.out); InputReader reader = new InputReader(System.in)) {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        }
    }
} Main public static void main(String[] args) throws IOException {
        try (PrintWriter writer = new PrintWriter(System.out); InputReader reader = new InputReader(System.in)) {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        }
    } main {
        try (PrintWriter writer = new PrintWriter(System.out); InputReader reader = new InputReader(System.in)) {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        }
    } try (PrintWriter writer = new PrintWriter(System.out); InputReader reader = new InputReader(System.in)) {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        } {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        } PrintWriter writer = new PrintWriter(System.out) PrintWriter writer = new PrintWriter(System.out) new PrintWriter(System.out) InputReader reader = new InputReader(System.in) InputReader reader = new InputReader(System.in) new InputReader(System.in) int N = reader.readInt(); N reader.readInt() reader.readInt reader int[][] squares = new int[2][]; squares new int[2][] 2 squares[0] = reader.readIntsSplitByDelimiter(" ") squares[0] squares 0 reader.readIntsSplitByDelimiter(" ") reader.readIntsSplitByDelimiter reader " " squares[1] = reader.readIntsSplitByDelimiter(" ") squares[1] squares 1 reader.readIntsSplitByDelimiter(" ") reader.readIntsSplitByDelimiter reader " " int max = 0; max 0 for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            } {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            } int count = 0; count 0 for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                } int j = 0; int j = 0; j 0 j < N j N j++ j++ j {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                } {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                } if (i == j) {
                        count += squares[0][j];
                    } i == j i j {
                        count += squares[0][j];
                    } count += squares[0][j] count squares[0][j] squares[0] squares 0 j if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    } i > j i j {
                        count += squares[0][j];
                    } count += squares[0][j] count squares[0][j] squares[0] squares 0 j {
                        count += squares[1][j];
                    } count += squares[1][j] count squares[1][j] squares[1] squares 1 j max = Math.max(max, count) max Math.max(max, count) Math.max Math max count writer.println(max) writer.println writer max writer.flush() writer.flush writer String[] args args class InputReader implements Closeable, AutoCloseable {
    private final BufferedReader br;

    InputReader(InputStream inputStream) {
        this.br = new BufferedReader(new InputStreamReader(inputStream));
    }

    String readLine() throws IOException {
        return this.br.readLine();
    }

    int readInt() throws IOException {
        return Integer.parseInt(this.readLine());
    }

    long readLong() throws IOException {
        return Long.parseLong(this.readLine());
    }

    String[] readStringsSplitByDelimiter(String delimiter) throws IOException {
        return this.readLine().split(delimiter);
    }

    int[] readIntsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        int[] ints = new int[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            ints[i] = Integer.parseInt(strings[i]);
        }

        return ints;
    }

    long[] readLongsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        long[] longs = new long[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            longs[i] = Long.parseLong(strings[i]);
        }

        return longs;
    }

    @Override
    public void close() throws IOException {
        this.br.close();
    }
} InputReader private final BufferedReader br; br InputReader(InputStream inputStream) {
        this.br = new BufferedReader(new InputStreamReader(inputStream));
    } InputReader {
        this.br = new BufferedReader(new InputStreamReader(inputStream));
    } this.br = new BufferedReader(new InputStreamReader(inputStream)) this.br this this.br new BufferedReader(new InputStreamReader(inputStream)) InputStream inputStream inputStream String readLine() throws IOException {
        return this.br.readLine();
    } readLine {
        return this.br.readLine();
    } return this.br.readLine(); this.br.readLine() this.br.readLine this.br this this.br int readInt() throws IOException {
        return Integer.parseInt(this.readLine());
    } readInt {
        return Integer.parseInt(this.readLine());
    } return Integer.parseInt(this.readLine()); Integer.parseInt(this.readLine()) Integer.parseInt Integer this.readLine() this.readLine this long readLong() throws IOException {
        return Long.parseLong(this.readLine());
    } readLong {
        return Long.parseLong(this.readLine());
    } return Long.parseLong(this.readLine()); Long.parseLong(this.readLine()) Long.parseLong Long this.readLine() this.readLine this String[] readStringsSplitByDelimiter(String delimiter) throws IOException {
        return this.readLine().split(delimiter);
    } readStringsSplitByDelimiter {
        return this.readLine().split(delimiter);
    } return this.readLine().split(delimiter); this.readLine().split(delimiter) this.readLine().split this.readLine() this.readLine this delimiter String delimiter delimiter int[] readIntsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        int[] ints = new int[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            ints[i] = Integer.parseInt(strings[i]);
        }

        return ints;
    } readIntsSplitByDelimiter {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        int[] ints = new int[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            ints[i] = Integer.parseInt(strings[i]);
        }

        return ints;
    } String[] strings = this.readLine().split(delimiter); strings this.readLine().split(delimiter) this.readLine().split this.readLine() this.readLine this delimiter int stringsLength = strings.length; stringsLength strings.length strings strings.length int[] ints = new int[stringsLength]; ints new int[stringsLength] stringsLength for (int i = 0; i < stringsLength; i++) {
            ints[i] = Integer.parseInt(strings[i]);
        } int i = 0; int i = 0; i 0 i < stringsLength i stringsLength i++ i++ i {
            ints[i] = Integer.parseInt(strings[i]);
        } {
            ints[i] = Integer.parseInt(strings[i]);
        } ints[i] = Integer.parseInt(strings[i]) ints[i] ints i Integer.parseInt(strings[i]) Integer.parseInt Integer strings[i] strings i return ints; ints String delimiter delimiter long[] readLongsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        long[] longs = new long[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            longs[i] = Long.parseLong(strings[i]);
        }

        return longs;
    } readLongsSplitByDelimiter {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        long[] longs = new long[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            longs[i] = Long.parseLong(strings[i]);
        }

        return longs;
    } String[] strings = this.readLine().split(delimiter); strings this.readLine().split(delimiter) this.readLine().split this.readLine() this.readLine this delimiter int stringsLength = strings.length; stringsLength strings.length strings strings.length long[] longs = new long[stringsLength]; longs new long[stringsLength] stringsLength for (int i = 0; i < stringsLength; i++) {
            longs[i] = Long.parseLong(strings[i]);
        } int i = 0; int i = 0; i 0 i < stringsLength i stringsLength i++ i++ i {
            longs[i] = Long.parseLong(strings[i]);
        } {
            longs[i] = Long.parseLong(strings[i]);
        } longs[i] = Long.parseLong(strings[i]) longs[i] longs i Long.parseLong(strings[i]) Long.parseLong Long strings[i] strings i return longs; longs String delimiter delimiter @Override
    public void close() throws IOException {
        this.br.close();
    } close {
        this.br.close();
    } this.br.close() this.br.close this.br this this.br Closeable AutoCloseable
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;

class Main {
    public static void main(String[] args) throws IOException {
        try (PrintWriter writer = new PrintWriter(System.out); InputReader reader = new InputReader(System.in)) {
            int N = reader.readInt();
            int[][] squares = new int[2][];
            squares[0] = reader.readIntsSplitByDelimiter(" ");
            squares[1] = reader.readIntsSplitByDelimiter(" ");

            int max = 0;
            for (int i = 0; i < N; i++) {
                int count = 0;
                for (int j = 0; j < N; j++) {
                    if (i == j) {
                        count += squares[0][j];
                    }

                    if (i > j) {
                        count += squares[0][j];
                    } else {
                        count += squares[1][j];
                    }
                }

                max = Math.max(max, count);
            }

            writer.println(max);
            writer.flush();
        }
    }
}

class InputReader implements Closeable, AutoCloseable {
    private final BufferedReader br;

    InputReader(InputStream inputStream) {
        this.br = new BufferedReader(new InputStreamReader(inputStream));
    }

    String readLine() throws IOException {
        return this.br.readLine();
    }

    int readInt() throws IOException {
        return Integer.parseInt(this.readLine());
    }

    long readLong() throws IOException {
        return Long.parseLong(this.readLine());
    }

    String[] readStringsSplitByDelimiter(String delimiter) throws IOException {
        return this.readLine().split(delimiter);
    }

    int[] readIntsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        int[] ints = new int[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            ints[i] = Integer.parseInt(strings[i]);
        }

        return ints;
    }

    long[] readLongsSplitByDelimiter(String delimiter) throws IOException {
        String[] strings = this.readLine().split(delimiter);

        int stringsLength = strings.length;
        long[] longs = new long[stringsLength];
        for (int i = 0; i < stringsLength; i++) {
            longs[i] = Long.parseLong(strings[i]);
        }

        return longs;
    }

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