import sys
from collections import defaultdict

MOD = 10**9 + 7

def main():
    N = int(sys.stdin.readline())
    A = [int(sys.stdin.readline()) for _ in range(N)]
    
    freq = defaultdict(int)
    for a in A:
        freq[a] += 1
    
    # Compute the generating function
    gf = [1]
    for v in freq:
        m = freq[v]
        new_gf = [0] * (len(gf) + 1)
        for k in range(len(gf)):
            new_gf[k] = (new_gf[k] + gf[k]) % MOD
            new_gf[k+1] = (new_gf[k+1] + gf[k] * m) % MOD
        gf = new_gf
    
    # Precompute factorials
    fact = [1] * (N + 1)
    for i in range(1, N + 1):
        fact[i] = fact[i-1] * i % MOD
    
    # Compute the inclusion-exclusion sum
    ans = 0
    for k in range(len(gf)):
        fk = gf[k]
        if fk == 0:
            continue
        rem = N - k
        if rem < 0:
            continue
        term = fk * fact[rem] % MOD
        if k % 2 == 1:
            term = (-term) % MOD
        ans = (ans + term) % MOD
    print(ans % MOD)

if __name__ == "__main__":
    main()