import java.util.Scanner;
public class arr{
    public static void main(String[] args){
        Scanner sc  = new Scanner(System.in);
        int len = sc.nextInt();
        int l1=0,l2=0,ind=0;
        if(len<2){
            System.out.print("Invalid input");
            return;
        }
        int[] arr = new int[len];
        for(int i = 0; i< len; i++){
             if(!z.hasNextInt()){
                System.out.print("Invalid input");
                return;
            }
            arr[i] = sc.nextInt();
        }
            for(int i = 0; i< len; i++){
               
                if(arr[i]>l1){
                    l1=arr[i];
                    ind = i;
                }
            
        }
        for(int j = 0; j< len; j++){
            if(arr[j]>l2){
                if(j!=ind){
                    l2=arr[j];
                    
                }
                }
            
        }
        if(l1==l2){
            System.out.print("Invalid input");
            return;
        }
        System.out.print(l2);
    }
}