source_code: import java.io.*;
  import java.util.*;
  import java.math.*;
  
  public class Main2 {
      public static void main(String[] args) throws Exception {
          new Main2().run();
      }
  
      public void solve() throws Exception {
          n = nextInt();
          int a[]= new int[n], pos = 1;
          for(int i=0; i<n; i++)
              a[i] = nextInt();
          Arrays.sort(a);
          if(n == 1){
              out.println("NO"); return;
          }
          boolean has = false;
          for(; pos<n; pos++){
              if(a[pos] != a[0]){
                  has = true;
                  break;
              }
          }
          if(!has){
              out.println("NO");
          }
          else{
              out.println(a[pos]);
          }
      }
      public int n, m;
  
      public void run() throws Exception {
          inter = new StreamTokenizer(new BufferedReader(new InputStreamReader(
                  System.in)));
          in = new BufferedReader(new InputStreamReader(System.in));
          out = new PrintWriter(new OutputStreamWriter(System.out));
          solve();
          out.flush();
      }
      public BufferedReader in;
      public StreamTokenizer inter;
      public PrintWriter out;
  
      public int nextInt() throws Exception {
          inter.nextToken();
          return (int) inter.nval;
      }
      public String nextLine() throws Exception{
          return in.readLine();
      }
  }
  