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.math.BigDecimal;
import java.util.AbstractMap;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.TreeSet;

public class Main {
	
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        
        Solver solver = new Solver();
        solver.solve(1, in, out);
        
        out.close();
    }
    
    // ======================================================================
    // 1 <= R, C <= 50  : R = 行数　　C = 列数
    // Sy, Sx = スタート、　　Gy, Gx = ゴール
    // C(y, x) :  . = 道　　# = 壁
    //
    // スタートからゴールへの最小手数は？
    //
    static class Solver {
    	int MOD = 1000000007;

    	int[] c;
    	public void solve(int testNumber, MyInput in, PrintWriter out) {
    		int N = in.nextInt();
    		boolean g_flg;
    		if(N % 2 == 0)	g_flg = true;
    		else			g_flg = false;
    		c = new int[N];
    		for(int i=1; i < N; i+=2) {
    			c[N - i] = 2;
//    			out.println("c[" + (N-i) + "] = 2");
    		}
    		if(!g_flg) {
    		    c[0] = 1;
//    			out.println("c[0] = 1");
    		}
    		int a;
    		boolean g_flg2;
    		int ans = 1;
    		for(int i=0; i < N; i++) {
    			a = in.nextInt();
    			g_flg2 = (a % 2 == 0);
    			if((g_flg && a == 0) || a > N-1 || c[a] <= 0
    					|| (g_flg && g_flg2) || (!g_flg && !g_flg2)) {
    				ans = 0;
//    				out.println("1  ans = 0");
    				break;
    			}
    			c[a]--;
    		}
    		if(ans != 0) {
	    		for(int i=1; i <= N; i+=2) {
	    			if(c[N - i] != 0) {
	    				ans = 0;
//        				out.println("2  ans = 0");
	    				break;
	    			}
	    		}
    		}
    		if(ans != 0) {
    			for(int i = 0; i < N/2; i++) {
    				ans = (ans * 2) % MOD;
    			}
    		}
            out.println(ans);
        }
    }
    // ======================================================================
    static class Pair<K, V> extends AbstractMap.SimpleEntry<K, V> {
        /** serialVersionUID. */
        private static final long serialVersionUID = 6411527075103472113L;

        public Pair(final K key, final V value) {
            super(key, value);
        }
     }    
    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];
 
        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }
 
        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }
 
        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }
 
        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }
 
        public String nextString() {
        	String ret = new String(nextDChar()).trim();
            return ret;
        }
 
        public char[] nextDChar() {
            int len = 0;
            len = reads(len, isSpace);
            char[] ret = new char[len + 1];
            for (int i=0; i < len; i++)		ret[i] = str[i];
            ret[len] = 0x00;
            return ret;
        }
 
        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }
 
        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }
 
        static class EndOfFileRuntimeException extends RuntimeException {
        }
    }
}


Measured memory_bytes: 25172