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  
    
25
35
43
38
33
47
44
40
36
41
42
33
30
49
42
62
39
40
35
43
31
42
46
42
34
33
 47
20
21
16
18
24
20
25
13
20
22
26
24
17
18
21
22
21
23
17
15
24
19
18
21
20
19
26
25
20
17
17
17
26
32
20
21
25
28
24
21
21
17
28
20
20
31
19
 3
343
317
337
 1
5
 10
100
100
100
100
100
100
100
100
100
100
 1
1
 13
67
75
76
80
69
86
75
86
81
84
73
72
76
 5
10
10
10
10
10
 11
291
381
126
39
19
20
3
1
20
45
2

362689152
 295545118
 691446102
 1
 12520708
 1
 232242896
 425711769
 902382672

import java.util.*;
import java.math.*;
import java.io.*;
public class Luck{
	public static InputReader sc;
    public static PrintWriter out;
    public static final long MOD = (long)1e9 + 7L;
    public static void main(String[] args){
    	sc=new InputReader(System.in);	
    	out=new PrintWriter(System.out);
    	long[][] dp=new long[1010][1010];
    	dp[0][0]=1L;
    	for(int i=1;i<1010;i++){
    		dp[i][0]=1L;
    		for(int j=1;j<=i;j++){
    			dp[i][j]=(dp[i-1][j]+dp[i-1][j-1])%MOD;
    		}
    	}
    	int n=sc.nextInt();
    	int total=0;
    	long res=1L;
    	for(int i=0;i<n;i++){
    		int c=sc.nextInt();
    		res=(res*dp[total+c-1][c-1])%MOD;
    		total+=c;
    	}
    	out.println(res);
    	out.close();
    }
    
//    static class Pair{
//    	String x;
//    	int y;
//    	Pair(){
//    		this.x="";
//    		this.y=-1;
//    	}
//    	Pair(String profit,int val,int count){
//    		this.x=profit;
//    		this.y=val;
//    	}
//    	public static Comparator<Pair> Val=new Comparator<Pair>(){
//    		public int compare(Pair p1,Pair p2){
//    			if(p1.x==p2.y){
//    				return p1.y-p2.y;
//    			}
//    			return (int)p1.x-(int)p2.x;
//    		}
//    	};
//    	public int hashCode() {
//    		final int prime = 31;
//    		int result = 1;
//    		result = prime * result + x;
//    		result = prime * result + x;
//    		return result;
//    	}
//    	public boolean equals(Object obj){
//    		if (this == obj)
//    	        return true;
//    	    if (!(obj instanceof Pair)) {
//    	        return false;
//    	    }
//    	 
//    	    Pair p = (Pair) obj;
//    	    if(p.x!=this.x){
//    	    	return false;
//    	    }
//    	    else if(p.y!=p.y){
//    	    	return false;
//    	    }
//    	    return true;
//    	}
//    }
    static class DisjointSet{
    	int n;
    	int[] par;
    	int[] rank;
    	DisjointSet(int n){
    		this.n=n;
    		this.par=new int[n];
    		this.rank=new int[n];
    		makeSet();
    	}
    	void makeSet(){
    		for(int i=0;i<n;i++){
    			par[i]=i;
    			rank[i]=1;
    		}
    	}
    	void union(int x,int y){
    		int parX=parent(x);
    		int parY=parent(y);
    		if(parX!=parY){
    			if(rank[parX]>=rank[parY]){
    				rank[parX]+=rank[parY];
    				rank[parY]=0;
    				par[parY]=parX;
    			}
    			else{
    				rank[parY]+=rank[parX];
    				rank[parX]=0;
    				par[parX]=parY;
    			}
    		}
    	}
    	int parent(int c){
    		int i=c;
    		while(i!=par[i]){
    			i=par[i];
    		}
    		return i;
    	}
    }
    static int gcd(int a,int b){
    	if(b==0){
    		return a;
    	}
    	return gcd(b,a%b);
    	
    }
    static int lcm(int a,int b){
    	int g;
    	if(a<b){
    		g=gcd(b,a);
    	}
    	else{
    		g=gcd(a,b);
    	}
    	return (a*b)/g;
    }
    static long bigmod ( long a, long p, long m ) {
        long res = 1 % m, x = a % m;
        while ( p>0 ) {
            if ( (p & 1)==1 ) res = ( res * x ) % m;
            x = ( x * x ) % m; p >>= 1;
        }
        return res;
    }
    static boolean isPrime(int n){
    	 if (n == 2)
    	        return true;
    	    for (long i = 2; i * i <= n; i++) {
    	        if (n % i == 0)
    	            return false;
    	    }
    	    return true;
    }
    
    static void shuffle(int[] A){
    	for(int i=A.length-1;i>0;i--){
    		int j=(int)(Math.random()*(i+1));
    		int temp=A[j];
    		A[j]=A[i];
    		A[i]=temp;
    	}
    }
    
//	public static class Node implements Comparable<Node>{
//	    int u;
//	    int v;
//	    public Node(){
//	    	;
//	    }
//	    public Node (int u, int v) {
//	    	this.u = u;
//	        this.v = v;
//	    }
//	    
//	    public void print() {
//	        out.println(v + " " + u + " ");
//	    }
//	   
//	    public int compareTo(Node n1){
//	    	return this.u-n1.u;
//	    }
//	}
	public static long pow(long base,long exp,long mod){
		if(exp==0){
			return 1;
		}
		if(exp==1){
			return base;
		}
		long temp=exp/2;
		long val=pow(base,temp,mod);
		long result=val*val;
		result=(result%mod);
		long AND=exp&1;
		if(AND==1){
			result*=base;
			result=(result%mod);
		}
		return result;
	}
	public static BigInteger pow(BigInteger base, BigInteger exp) {
	    if(exp.equals(new BigInteger(String.valueOf(0)))){
	        return new BigInteger(String.valueOf(1));
	    }    
	    if(exp.equals(new BigInteger(String.valueOf(1))))
	        return base;
	    BigInteger temp=exp.divide(new BigInteger(String.valueOf(2)));
	    BigInteger val = pow(base, temp);
	    BigInteger result = val.multiply(val);
	    result=result.remainder(new BigInteger(String.valueOf(MOD)));
	    BigInteger AND=exp.and(new BigInteger(String.valueOf(1)));
	    if(AND.equals(new BigInteger(String.valueOf(1)))){
	        result = result.multiply(base);
	        result=result.remainder(new BigInteger(String.valueOf(MOD)));
	    }    
	    return result;
	}
	    
	static class InputReader {

	    private InputStream stream;
	    private byte[] buf = new byte[8192];
	    private int curChar, snumChars;
	    private SpaceCharFilter filter;

	    public InputReader(InputStream stream) {
	        this.stream = stream;
	    }

	    public int snext() {
	        if (snumChars == -1)
	            throw new InputMismatchException();
	        if (curChar >= snumChars) {
	            curChar = 0;
	            try {
	                snumChars = stream.read(buf);
	            } catch (IOException e) {
	                throw new InputMismatchException();
	            }
	            if (snumChars <= 0)
	                return -1;
	        }
	        return buf[curChar++];
	    }

	    public int nextInt() {
	        int c = snext();
	        while (isSpaceChar(c))
	            c = snext();
	        int sgn = 1;
	        if (c == '-') {
	            sgn = -1;
	            c = snext();
	        }
	        int res = 0;
	        do {
	            if (c < '0' || c > '9')
	                throw new InputMismatchException();
	            res *= 10;
	            res += c - '0';
	            c = snext();
	        } while (!isSpaceChar(c));
	        return res * sgn;
	    }

	    public long nextLong() {
	        int c = snext();
	        while (isSpaceChar(c))
	            c = snext();
	        int sgn = 1;
	        if (c == '-') {
	            sgn = -1;
	            c = snext();
	        }
	        long res = 0;
	        do {
	            if (c < '0' || c > '9')
	                throw new InputMismatchException();
	            res *= 10;
	            res += c - '0';
	            c = snext();
	        } while (!isSpaceChar(c));
	        return res * sgn;
	    }

	    public int[] nextIntArray(int n) {
	        int a[] = new int[n];
	        for (int i = 0; i < n; i++)
	            a[i] = nextInt();
	        return a;
	    }

	    public String readString() {
	        int c = snext();
	        while (isSpaceChar(c))
	            c = snext();
	        StringBuilder res = new StringBuilder();
	        do {
	            res.appendCodePoint(c);
	            c = snext();
	        } 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 interface SpaceCharFilter {
	        public boolean isSpaceChar(int ch);
	    }
	}

}

