import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * Built using CHelper plug-in Actual solution is at the top
 */

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);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        }
    }

    static boolean permutation_2(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    }

    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 char nextChar() {
            return next().charAt(0);
        }

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

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

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

    }
} import java.io.BufferedReader; BufferedReader 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.OutputStream; OutputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.util.StringTokenizer; StringTokenizer java.util 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);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        }
    }

    static boolean permutation_2(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    }

    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 char nextChar() {
            return next().charAt(0);
        }

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

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

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

    }
} 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);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out InputReader in = new InputReader(inputStream); in new InputReader(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) Task solver = new Task(); solver new Task() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static boolean permutation_2(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    } permutation_2 {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    } if (s.length() != t.length()) {
            return false;
        } s.length() != t.length() s.length() s.length s t.length() t.length t {
            return false;
        } return false; false int[] letters = new int[256]; letters new int[256] 256 char[] s_array = s.toCharArray(); s_array s.toCharArray() s.toCharArray s for (char c : s_array) {
            letters[c]++;
        } char c s_array {
            letters[c]++;
        } {
            letters[c]++;
        } letters[c]++ letters[c] letters c for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        } int i = 0; int i = 0; i 0 i < t.length() i t.length() t.length t i++ i++ i {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        } {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        } int c = (int) t.charAt(i); c (int) t.charAt(i) t.charAt t i if (--letters[c] < 0) {
                return false;
            } --letters[c] < 0 --letters[c] letters[c] letters c 0 {
                return false;
            } return false; false return true; true String s s String t t static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        }
    } Task public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        } solve {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        } int n = in.nextInt(); n in.nextInt() in.nextInt in int[] arr = new int[n]; arr new int[n] n for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                arr[i] = in.nextInt();
            } {
                arr[i] = in.nextInt();
            } arr[i] = in.nextInt() arr[i] arr i in.nextInt() in.nextInt in int ans = 0; ans 0 while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            } true {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            } int count = 0; count 0 for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                } {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                } if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    } arr[i] > 0 arr[i] arr i 0 {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } arr[i] = arr[i] - 1 arr[i] arr i arr[i] - 1 arr[i] arr i 1 if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        } i < n - 1 && arr[i + 1] == 0 i < n - 1 i n - 1 n 1 arr[i + 1] == 0 arr[i + 1] arr i + 1 i 1 0 {
                            break;
                        } break; if (arr[i] == 0) {
                        count++;
                    } arr[i] == 0 arr[i] arr i 0 {
                        count++;
                    } count++ count if (count == n) {
                    break;
                } count == n count n {
                    break;
                } break; ans++ ans out.println(ans) out.println out ans int testNumber testNumber InputReader in in PrintWriter out out 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 char nextChar() {
            return next().charAt(0);
        }

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

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

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

    } InputReader public BufferedReader reader; reader public StringTokenizer tokenizer; tokenizer public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        } InputReader {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        } reader = new BufferedReader(new InputStreamReader(stream), 32768) reader new BufferedReader(new InputStreamReader(stream), 32768) tokenizer = null tokenizer null InputStream stream stream public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        } next {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        } while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            } tokenizer == null || !tokenizer.hasMoreTokens() tokenizer == null tokenizer null !tokenizer.hasMoreTokens() tokenizer.hasMoreTokens() tokenizer.hasMoreTokens tokenizer {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            } try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                } catch (IOException e) {
                    throw new RuntimeException(e);
                } IOException e {
                    throw new RuntimeException(e);
                } throw new RuntimeException(e); new RuntimeException(e) {
                    tokenizer = new StringTokenizer(reader.readLine());
                } tokenizer = new StringTokenizer(reader.readLine()) tokenizer new StringTokenizer(reader.readLine()) return tokenizer.nextToken(); tokenizer.nextToken() tokenizer.nextToken tokenizer public char nextChar() {
            return next().charAt(0);
        } nextChar {
            return next().charAt(0);
        } return next().charAt(0); next().charAt(0) next().charAt next() next 0 public int nextInt() {
            return Integer.parseInt(next());
        } nextInt {
            return Integer.parseInt(next());
        } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next public double nextDouble() {
            return Double.parseDouble(next());
        } nextDouble {
            return Double.parseDouble(next());
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public long nextLong() {
            return Long.parseLong(next());
        } nextLong {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next 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);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        }
    }

    static boolean permutation_2(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    }

    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 char nextChar() {
            return next().charAt(0);
        }

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

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

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

    }
} 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);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        }
    }

    static boolean permutation_2(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    }

    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 char nextChar() {
            return next().charAt(0);
        }

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

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

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

    }
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * Built using CHelper plug-in Actual solution is at the top
 */

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);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }

    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            int ans = 0;
            while (true) {
                int count = 0;
                for (int i = 0; i < n; i++) {
                    if (arr[i] > 0) {
                        arr[i] = arr[i] - 1;
                        if (i < n - 1 && arr[i + 1] == 0) {
                            break;
                        }
                    } else if (arr[i] == 0) {
                        count++;
                    }
                }
                if (count == n) {
                    break;
                }
                ans++;
            }
            out.println(ans);
        }
    }

    static boolean permutation_2(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }

        int[] letters = new int[256];

        char[] s_array = s.toCharArray();
        for (char c : s_array) {
            letters[c]++;
        }

        for (int i = 0; i < t.length(); i++) {
            int c = (int) t.charAt(i);
            if (--letters[c] < 0) {
                return false;
            }
        }
        return true;
    }

    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 char nextChar() {
            return next().charAt(0);
        }

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

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

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

    }
}
