source_code: 
  
  import java.io.InputStreamReader;
  import java.util.Arrays;
  import java.util.Scanner;
  
  public class A {
  
  	/**
  	 * @param args
  	 */
  	public static void main(String[] args) {
  		Scanner s = new Scanner(new InputStreamReader(System.in));
  		int n = s.nextInt();	
  		int [] ar = new int[n];
  		for (int i = 0; i < n ; i++) {
  			ar[i] = s.nextInt();
  	 	}
  		if(ar.length == 1){
  			System.out.println("NO");
  		}else{
  			Arrays.sort(ar);
  			int num = ar[0];
  			boolean flag = false;
  			for (int i = 1; i < ar.length; i++) {
  				if(ar[i]!= num){
  					System.out.println(ar[i]);
  					flag = true;
  					break;
  				}
  			}
  			if(!flag)
  				System.out.println("NO");
  		}
  
  	}
  
  }
  