MOD = 10**9+7
SIZE = 6000
fac = [0]*SIZE
fac[0] = fac[1] = 1
for i in range(2,SIZE):
    fac[i] = fac[i-1]*i%MOD

n,*a = map(int,open(0).read().split())
r = [0]*n
for i in a: r[i] += 1
dp = [1]
for ri in r:
    dp += [0]
    for i in range(len(dp)-1,0,-1):
        dp[i] += ri*dp[i-1]
        dp[i] %= MOD
ans = 0
sgn = 1
for i,xi in enumerate(dp):
    ans += sgn*xi*fac[n-i]%MOD
    sgn *= -1
print(ans%MOD)