import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.InputStream;

/**
 * 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);
        OutputWriter out = new OutputWriter(outputStream);
        TaskA solver = new TaskA();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskA {
        long MOD = 998244353;

        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int N = in.nextInt();
            Integer D[] = in.nextIntArray(N);
            int a[] = new int[N];
            for (int i = 0; i < N; i++) {
                a[D[i]]++;
            }
            if (a[0] != 1 || D[0] != 0) {
                out.printLine(0);
                return;
            }
            long ans = 1;
            int count = 1;

            for (int i = 1; i < N; i++) {
                if (count != N) {
                    if (a[i] == 0) {
                        out.printLine(0);
                        return;
                    }
                } else {
                    break;
                }
                long p = fastExponentization(a[i - 1], a[i]);
                ans = (ans * p) % MOD;
                count += a[i];
            }
            out.printLine(ans);
        }

        public long fastExponentization(long base, long exp) {
            long result = 1;
            while (exp > 0) {
                if (exp % 2 == 1) {
                    result = (result * base) % MOD;
                }
                base = (base * base) % MOD;
                exp /= 2;
            }
            return result % MOD;
        }

    }

    static class InputReader {
        BufferedReader in;
        StringTokenizer tokenizer = null;

        public InputReader(InputStream inputStream) {
            in = new BufferedReader(new InputStreamReader(inputStream));
        }

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

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

        public Integer[] nextIntArray(int size) {
            Integer array[] = new Integer[size];
            for (int i = 0; i < size; i++) {
                array[i] = nextInt();
            }
            return array;
        }

    }

    static class OutputWriter {
        PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void printLine(Object... objects) {
            print(objects);
            writer.println();
        }

        public void close() {
            writer.close();
        }

    }
}



Measured memory_bytes: 35864