import java.io.*;
import java.math.*;
public class Main {
    public static void main(String args[])throws IOException
    {
        StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        BigInteger data[]=new BigInteger[30];
        int [] x = new int[30];
        while(true){

            st.nextToken();
            int n=(int)st.nval;
            if( n == 0 ) break ;
            int sum = 0 ;
            for(int i=1;i<=n;i++)
            {
                st.nextToken();
                x[i]=(int)st.nval;
                sum += x[i];
            }

            BigInteger res=BigInteger.ONE;

            for( int i = 1 ; i <= sum ; ++i ){
                res = res.multiply(BigInteger.valueOf(i));
            }
            for( int i = 1 ; i <= n ; ++i ){
                for( int j = 1 ; j <= x[i] ; ++j ){
                    res = res.divide( BigInteger.valueOf(j) );
                }
            }
            out.println(res);
        }
        out.close();
    }
}