import bisect

n, m, q = map(int, input().split())
pairs = [tuple(map(int, input().split())) for _ in range(q)]
pairs.sort()
groups = []
current_a = None
current_ys = []
for a, b in pairs:
    if a != current_a:
        if current_a is not None:
            groups.append(current_ys)
        current_a = a
        current_ys = []
    current_ys.append(b)
if current_ys:
    groups.append(current_ys)

dp = []
for ys in groups:
    if not dp:
        if ys:
            dp.append(ys[0])
    else:
        last_y = dp[-1]
        idx = bisect.bisect_right(ys, last_y)
        if idx < len(ys):
            dp.append(ys[idx])

print(len(dp))