const MOD: usize = 1e9 as usize + 7;

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    if *a.iter().min().unwrap() == 0 {
        println!("-1");
        return;
    }
    let mut result = 1usize;
    for i in 0..n {
        if a[i] >= 4 {
            println!("{}", MOD);
            return;
        } else if a[i] == 3 {
            for _ in 0..6 {
                result = result * 3;
            }
        } else if a[i] == 2 {
            for _ in 0..2 {
                result = result * 2;
            }
        }
        if result > MOD {
            println!("{}", MOD);
            return;
        }
    }
    println!("{}", MOD % result);;
}