f.all

#include <iostream>
using namespace std;
int main()
{
    int x;
    cin>>x;
    const int Size=x;
    long long seq[Size],N1,N2;
    for(int i=0;i<Size;i++){
        cin>>seq[i];
            if(i==1){
                N1=seq[0];
                N2=seq[1];
                if(N1<N2){
                    swap(N1,N2);
                    }
                }
           if(i>1){
                if(seq[i]>=N1){
                    N2=N1;
                    N1=seq[i];
                    }
                else{
                if(seq[i]>N2)
                    N2=seq[i];
                    }
                }
            }
    cout<<N1*N2;
}