from math import *
fin = open("input.txt","r")
fout = open("output.txt","w")
n, m, k = map(int, fin.readline().split())
op = [0] * n
ans = 0
for i in range (0, k):
    a, b = map(int, fin.readline().split())
    if b >= 2 * n + 1  and a <= n:
        if op[a - 1] == 0:
            op[a - 1] = 1
            ans += 1

print(factorial(ans - 1), file = fout)
fout.close
fin.close