/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
 
public static void main(String[] args){
	Scanner s=new Scanner(System.in);
	int a=s.nextInt();
	String output="",input="";
	String[] b=new String[a];
	for(int i=0;i<a;i++)
	{
		b[i]=s.next();
	    input=input+b[i];
	}
	output=otp(input,a,b);
	System.out.println(output);
}
public static String otp(String input,int a,String b[]){
 
	int o=0;
	String output="";
	String[] on=new String[100];
	for(int i=0;i<a;i++)
	{
		char[] q=b[i].toCharArray();
		for(int j=0;j<q.length-1;j++)
		{
			on[o]="";
		    on[o]=q[j]+""+q[j+1];
		    ++o;
		}
	}
	Arrays.sort(on,0,o);
	output=output+on[o-1];
	char[] in=input.toCharArray();
	Arrays.sort(in);
	int m=0;
	m=in[2]+in[in.length-1];
	m=m-48-48;
	output=output+m;
	return output;
}
	}
 

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

ODUgNjU4IDgwMSA0NTk=

85 658 801 459