package no389;

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {
	public static long MOD = 1000000007;
	public static void main(String[] args) {
		IO io = new IO();
		int n = io.nextInt();
		ArrayList<Integer> h = new ArrayList<>();
		while(io.hasNext()) {
			h.add(io.nextInt());
		}
		if (h.size() == 1 && h.get(0) == 0) {
			System.out.println(1);
			return;
		}
		int sum = 0;
		for(int x: h) {
			sum += x;
		}
		int m = h.size();
		int free = n - (sum + m - 1);
		if (free < 0) {
			System.out.println("NA");
			return;
		}
//		System.out.println(m + "." + free);
		//ans = fact[free+m-1] / fact[free] / fact[m-1]
		long[] fact = Mod.factorialArray(n+1, MOD);
		long[] factInv = Mod.factorialInverseArray(n+1, MOD, Mod.inverseArray(n+1, MOD));
		System.out.println(fact[free+m] * factInv[free] % MOD * factInv[m] % MOD);
	}

}
class Mod {
	public static long[] inverseArray(int maxN,long modP) {
		long[] inv = new long[maxN+1];
		inv[1] = 1;
		for(int i=2;i<=maxN;i++) {
			inv[i] = modP - (modP / i) * inv[(int) (modP%i)] % modP;
		}
		return inv;
	}
	public static long[] factorialArray(int maxN,long mod) {
		long[] fact = new long[maxN+1];
		fact[0] = 1 % mod;
		for(int i=1;i<=maxN;i++) {
			fact[i] = fact[i-1] * i % mod;
		}
		return fact;
	}
	public static long[] factorialInverseArray(int maxN,long modP,long[] inverseArray) {
		long[] factInv = new long[maxN+1];
		factInv[0] = 1;
		for(int i=1;i<=maxN;i++) {
			factInv[i] = factInv[i-1] * inverseArray[i] % modP;
		}
		return factInv;
	}
}

class IO extends PrintWriter {
	private final InputStream in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;
	
	public IO() { this(System.in);}
	public IO(InputStream source) { super(System.out); this.in = source;}
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	private static boolean isNewLine(int c) { return c == '\n' || c == '\r';}
	public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
	public boolean hasNextLine() { while(hasNextByte() && isNewLine(buffer[ptr])) ptr++; return hasNextByte();}
	public String next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public char[] nextCharArray(int len) {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		char[] s = new char[len];
		int i = 0;
		int b = readByte();
		while(isPrintableChar(b)) {
			if (i == len) {
				throw new InputMismatchException();
			}
			s[i++] = (char) b;
			b = readByte();
		}
		return s;
	}
	public String nextLine() {
		if (!hasNextLine()) {
			throw new NoSuchElementException();
		}
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while(!isNewLine(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
			throw new NumberFormatException();
		}
		return (int) nl;
	}
	public char nextChar() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		return (char) readByte();
	}
	public double nextDouble() { return Double.parseDouble(next());}
	public int[] nextIntArray(int n) { int[] a = new int[n]; for(int i=0;i<n;i++) a[i] = nextInt(); return a;}
	public long[] nextLongArray(int n) { long[] a = new long[n]; for(int i=0;i<n;i++) a[i] = nextLong(); return a;}
	public double[] nextDoubleArray(int n) { double[] a = new double[n]; for(int i=0;i<n;i++) a[i] = nextDouble(); return a;}
	public void nextIntArrays(int[]... a) { for(int i=0;i<a[0].length;i++) for(int j=0;j<a.length;j++) a[j][i] = nextInt();}
	public int[][] nextIntMatrix(int n,int m) { int[][] a = new int[n][]; for(int i=0;i<n;i++) a[i] = nextIntArray(m); return a;}
	public char[][] nextCharMap(int n,int m) { char[][] a = new char[n][]; for(int i=0;i<n;i++) a[i] = nextCharArray(m); return a;}
	public void close() { super.close(); try {in.close();} catch (IOException e) {}}
}