mod = 10**9 + 7

N = int(input())
A = [int(input()) for _ in range(N)]

from collections import defaultdict

# Count the occurrences of each disliked number
cnt = defaultdict(int)
for a in A:
    cnt[a] += 1

# List of unique disliked numbers that appear at least once
vals = list(cnt.keys())

# Precompute factorial modulo mod
fact = [1] * (N + 1)
for i in range(1, N + 1):
    fact[i] = fact[i - 1] * i % mod

# Initialize DP: dp[k] is the number of ways to choose k distinct values
dp = [0] * (N + 1)
dp[0] = 1

for v in vals:
    c = cnt[v]
    # Update dp in reverse to avoid overwriting values we still need to process
    for j in range(N, -1, -1):
        if dp[j] and j < N:
            dp[j + 1] = (dp[j + 1] + dp[j] * c) % mod

# Calculate the result using inclusion-exclusion principle
result = 0
for k in range(0, N + 1):
    if dp[k] == 0:
        continue
    remaining = N - k
    if remaining < 0:
        continue
    # Current term: (-1)^k * dp[k] * (remaining)!
    term = dp[k] * fact[remaining] % mod
    if k % 2 == 1:
        term = (mod - term) % mod  # Convert to positive mod value
    result = (result + term) % mod

print(result)