import java.util.Scanner;

public class Main {
    public static void main(String args[]){
        Scanner stdIn = new Scanner(System.in);
        
        int n = stdIn.nextInt();
        //int b = stdIn.nextInt();
        long p[] = new long[n];
        //String s = stdIn.next();
        //char c[] = s.toCharArray();
        long sum = 1;
        //boolean flag = true;
        
        for(int i = 0; i < n; i++){
            sum *= stdIn.nextInt();
        }
        
        while(true){
            String s = String.valueOf(sum);
            char c[] = s.toCharArray();
            
            sum = 0;
            
            for(int i = 0; i < s.length(); i++){
                sum += c[i] - 48;
            }
            
            if(sum <= 9){
                break;
            }
        }
        

        
        System.out.println(sum);
        
        //System.out.println();
        //System.out.print();
    }
}