// editor3

import java.util.*;
public class stones{
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        if(!sc.hasNextInt()){
            System.out.println("Invalid input");
            return;
        }
        int[] arr=new int[n];
        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
            if(arr[i]<0 || isdigit(arr[i])){
                System.out.println("Invalid input");
            return;
            }
        }
        int mul=1;
        for(int i=0;i<n;i++){
            mul*=arr[i];
        }
        System.out.println(mul);
    }
}