from heapq import *

N,M,Q = map(int,input().split())
l = [[] for _ in range(N)]
for _ in range(Q):
  a,b = map(int,input().split())
  a -= 1
  b -= 1
  l[a].append(b)

check = [False]*M
ans,before = 0,-1

for i in range(N):
  while l[i]:
    m = heappop(l[i])
    if check[m] or before >= m:
      continue
    before = m
    check[m] = True
    ans += 1
    break

print(ans)