//package round22;


import java.io.PrintWriter;
import java.io.StringReader;
import java.util.Arrays;
import java.util.Scanner;

public class A {
	private Scanner in;
	private PrintWriter out;
//	private String INPUT = "5 1 2 3 1 1";
	private String INPUT = "";
	
	public void solve()
	{
		int n = ni();
		int[] a = new int[n];
		for(int i = 0;i < n;i++){
			a[i] = ni();
		}
		Arrays.sort(a);
		for(int i = 1;i < n;i++){
			if(a[i] > a[i - 1]){
				out.println(a[i]);
				return;
			}
		}
		out.println("NO");
	}
	
	public void run() throws Exception
	{
		in = INPUT.isEmpty() ? new Scanner(System.in) : new Scanner(new StringReader(INPUT));
		out = new PrintWriter(System.out);
		
		solve();
		out.flush();
	}
	
	
	public static void main(String[] args) throws Exception
	{
		new A().run();
	}
	
	private int ni() { return Integer.parseInt(in.next()); }
	private static void tr(Object... o) { System.out.println(o.length == 1 ? o[0] : Arrays.toString(o)); }
}
