#include <bits/stdc++.h>
#include <fstream> 
 
using namespace std;
 
int main()
{
	int N,i,j,flag;
	cin>>N;  // No. of elements in the array
 
	int A[N+1];
	flag=1; // Flag initialization
 
	for(i=0;i<N;i++) // Input
		cin>>A[i];
 
	sort(A,A+N); // Sorting the Array
 
	for(i=N-2;i>=0;i--)
	{
		if(A[i]!=A[i+1])
		{
			cout<<A[i]<<endl; // Answer
			flag=0;  // We have encountered the second maximum unique element.
			break;
		}
	}
	if(flag)  // Flag will be 1 if all the elemts which is the special case here.
		cout<<0<<endl;
 
 
	return 0;
} 

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