use std::io::*;
use std::str::FromStr;

fn fact(x: i64) -> i64 {
    let mut ret = 1;
    for i in 1..=x {
        ret *= i;
    }
    ret
}

fn calc(n: i64, v: Vec<i64>) -> i64 {
    let mut ret = 1;
    for i in 0..n {
        let x = v[i as usize];
        if x == 0 {
            return -1;
        }
        if x >= 4 {
            return 1000_000_007_i64;
        }

        let mut p = 1;
        for _ in 0..fact(x) {
            p *= x;
        }
        ret *= p;
    }
    1000_000_007_i64 % ret
}

fn main() {
    let mut s = String::new();
    stdin().read_line(&mut s).ok();
    let mut itr = s.split_whitespace().map(|x| i64::from_str(x).unwrap());
    let n = itr.next().unwrap();

    s.clear();
    stdin().read_line(&mut s).ok();
    let mut itr = s.split_whitespace().map(|x| i64::from_str(x).unwrap());
    let mut v = Vec::new();
    for _i in 0..n {
        v.push(itr.next().unwrap());
    }

    println!("{}", calc(n, v));
}