Kyoya Ootori has a bag with n colored balls that are colored with k different colors. The colors are labeled from 1 to k. Balls of the same color are indistinguishable. He draws balls from the bag one by one until the bag is empty. He noticed that he drew the last ball of color i before drawing the last ball of color i + 1 for all i from 1 to k - 1. Now he wonders how many different ways this can happen. 

Input

The first line of input will have one integer k (1 ≤ k ≤ 1000) the number of colors.

Then, k lines will follow. The i-th line will contain ci, the number of balls of the i-th color (1 ≤ ci ≤ 1000).

The total number of balls doesn't exceed 1000.

Output

A single integer, the number of ways that Kyoya can draw the balls from the bag as described in the statement, modulo 1 000 000 007. 

Examples

Input

3
2
2
1


Output

3


Input

4
1
2
3
4


Output

1680

Note

In the first sample, we have 2 balls of color 1, 2 balls of color 2, and 1 ball of color 3. The three ways for Kyoya are: 
    
    
      
    1 2 1 2 3  
    1 1 2 2 3  
    2 1 1 2 3  
    
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.io.*;
import java.math.*;
public class Main7
{
	static class Pair
	{
		int x;
		int y;
		Pair(int x,int y)
		{
			this.x=x;
			this.y=y;
		}
	}
	static int mod=1000000007;
	public static int[] sort(int[] a)
	{
		int n=a.length;
		ArrayList<Integer> ar=new ArrayList<>();
		for(int i=0;i<a.length;i++)
		{
			ar.add(a[i]);
		}
		Collections.sort(ar);
		for(int i=0;i<n;i++)
		{
			a[i]=ar.get(i);
		}
		return a;
	}
	public static long pow(long a, long b)
    {
        long result=1;
        while(b>0)
        {
            if (b % 2 != 0)
            {
                result=(result*a)%mod;
                b--;
            } 
            a=(a*a)%mod;
            b /= 2;
        }   
        return result;
    }
	
    public static long gcd(long a, long b)
    {
        if (a == 0)
            return b;
        return gcd(b%a, a);
    }   
	public static long lcm(long a, long b)
	{
		return a*(b/gcd(a,b));
	}
	static ArrayList<ArrayList<Integer>> graph;
	static public void main(String args[])throws IOException
	{
		int tt=1;
		StringBuilder sb1=new StringBuilder();
		for(int ttt=1;ttt<=tt;ttt++)
		{
			int k=i();
			int[] a=new int[k];
			for(int i=0;i<k;i++)
				a[i]=i();
			long[] fact=new long[1001];
			fact[0]=1;
			for(int i=1;i<=1000;i++)
			{
				fact[i]=(fact[i-1]*i)%mod;
			}
			long[] inv=new long[1001];
			for(int i=0;i<=1000;i++)
			{
				inv[i]=pow(fact[i],mod-2);
			}
			long[] dp=new long[k+1];
			dp[1]=1;
			int totballs=a[0];
			for(int i=2;i<=k;i++)
			{
				totballs+=a[i-1];
				long tmp=1;
				tmp=tmp*fact[totballs-a[i-1]+1+a[i-1]-1-1];
				tmp=(tmp*inv[a[i-1]-1])%mod;
				tmp=(tmp*inv[totballs-a[i-1]+1+a[i-1]-1-1-a[i-1]+1])%mod;
				dp[i]=(dp[i-1]*tmp)%mod;
			}
			pln(dp[k]+"");
		}
		System.out.print(sb1.toString());
	}
	
	/**/
	static InputReader in=new InputReader(System.in);
	static OutputWriter out=new OutputWriter(System.out);
	public static long l()
	{
		String s=in.String();
		return Long.parseLong(s);
	}
	public static void pln(String value)
	{
		System.out.println(value);
	}
	public static int i()
	{
		return in.Int();
	}
	public static String s()
	{
		return in.String();
	}
}
	class InputReader 
	{
		private InputStream stream;
		private byte[] buf = new byte[1024];
		private int curChar;
		private int numChars;
		private SpaceCharFilter filter;
	 
		public InputReader(InputStream stream) {
			this.stream = stream;
		}
	 
		public int read() {
			if (numChars== -1)
				throw new InputMismatchException();
			if (curChar >= numChars) {
				curChar = 0;
				try {
					numChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (numChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}
	 
		public int Int() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}
	 
		public String String() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}
	 
		public boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}
	 
		public String next() {
			return String();
		}
	 
		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}
	 
	class OutputWriter {
		private final 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();
		}
	 
		public void flush() {
			writer.flush();
		}
	 
		}
	 
		class IOUtils {
	 
		public static int[] readIntArray(InputReader in, int size) {
			int[] array = new int[size];
			for (int i = 0; i < size; i++)
				array[i] = in.Int();
			return array;
		}
	 
	} 

