#!/usr/bin/env python3
n = int(input())
x = list(map(int, input().split()))
a = 0
b = 0
c = 0
r = 0
t = 0
for e in x:
    if e == 3: c += 1
for e in x:
    if e == 1: a += 1
    elif e == 2:
        b = t + a
        t += b
        r += b*c
    else:
        c -= 1
print(r%1000000007)