import java.util.Scanner;

public class No1237 {

	public static void main(String[] args) {
		
		Scanner scanner= new Scanner(System.in);
		int n = scanner.nextInt();
		int ans = 1 , p = (int)Math.pow(10, 9)+7;
		long ans2 = 1;
		
		int[] a = new int[n];
		for(int i = 0;i < n;i++) {
			a[i] = scanner.nextInt();
			if(a[i] == 0) {
				ans = -1;
				break;
			}else if(a[i] >=4) {
				ans= p;
			}else if(ans== p){
				continue;
			}else {
				
				switch (a[i]) {
				case 3: 
					ans2 *= 729;
					break;
				case 2:
					ans2 *= 4;
				}
				
				if(ans2 >= p) {
					ans = p;
				}
			}
			
		}
		
		scanner.close();
		
		if(ans != 1) {
			System.out.println(ans);
		}else {
			System.out.println(p % ans2);
		}
		

	}

}