Buggy python submission (verdict: Time Limit Exceeded):
import sys
h, w, n = [int(i) for i in sys.stdin.readline().split()]
m = 1000000007
fact = [1, 1]
for i in range(2, 200002):
    fact.append(fact[-1] * i)
inv = [pow(i, m - 2, m) for i in fact]
f = lambda i: fact[i[0] + i[1]] * inv[i[0]] * inv[i[1]] % m
dp = [0] * (n + 1)
p = [[int(i) - 1 for i in sys.stdin.readline().split()] for j in range(n)]
p = sorted(p + [[h - 1, w - 1]])
for i in range(n + 1):
    h1, w1 = p[i]
    tot = f([h1, w1])
    for j in range(i):
        if p[j][1] > w1:
            continue
        tot = (tot - dp[j] * f([h1 - p[j][0], w1 - p[j][1]]) % m) % m
    dp[i] = tot
print(dp[-1])

Fixed submission:
import sys
h, w, n = [int(i) for i in sys.stdin.readline().split()]
m = 1000000007
fact = [1, 1]
for i in range(2, 200002):
    fact.append(fact[-1] * i % m)
inv = [pow(i, m - 2, m) for i in fact]
f = lambda i: fact[i[0] + i[1]] * inv[i[0]] * inv[i[1]] % m
dp = [0] * (n + 1)
p = [[int(i) - 1 for i in sys.stdin.readline().split()] for j in range(n)]
p = sorted(p + [[h - 1, w - 1]])
for i in range(n + 1):
    h1, w1 = p[i]
    tot = f([h1, w1])
    for j in range(i):
        if p[j][1] > w1:
            continue
        tot = (tot - dp[j] * f([h1 - p[j][0], w1 - p[j][1]]) % m) % m
    dp[i] = tot
print(dp[-1])

Buggy python submission (verdict: Runtime Error):
import sys
h, w, n = [int(i) for i in sys.readline().split()]
m = 1000000007
fact = [1, 1]
for i in range(2, 200002):
    fact.append(fact[-1] * i)
inv = [pow(i, m - 2, m) for i in fact]
f = lambda i: fact[i[0] + i[1]] * inv[i[0]] * inv[i[1]] % m
dp = [0] * (n + 1)
p = [[int(i) - 1 for i in sys.readline().split()] for j in range(n)]
p = sorted(p + [[h - 1, w - 1]])
for i in range(n + 1):
    h1, w1 = p[i]
    tot = f([h1, w1])
    for j in range(i):
        if p[j][1] > w1:
            continue
        tot = (tot - dp[j] * f([h1 - p[j][0], w1 - p[j][1]]) % m) % m
    dp[i] = tot
print(dp[-1])

Fixed submission:
import sys
h, w, n = [int(i) for i in sys.stdin.readline().split()]
m = 1000000007
fact = [1, 1]
for i in range(2, 200002):
    fact.append(fact[-1] * i % m)
inv = [pow(i, m - 2, m) for i in fact]
f = lambda i: fact[i[0] + i[1]] * inv[i[0]] * inv[i[1]] % m
dp = [0] * (n + 1)
p = [[int(i) - 1 for i in sys.stdin.readline().split()] for j in range(n)]
p = sorted(p + [[h - 1, w - 1]])
for i in range(n + 1):
    h1, w1 = p[i]
    tot = f([h1, w1])
    for j in range(i):
        if p[j][1] > w1:
            continue
        tot = (tot - dp[j] * f([h1 - p[j][0], w1 - p[j][1]]) % m) % m
    dp[i] = tot
print(dp[-1])

Buggy python submission (verdict: Time Limit Exceeded):
h, w, n = [int(i) for i in input().split(" ")]
m = 1000000007
fact = [1, 1]
for i in range(2, 250000):
    fact.append(fact[-1] * i)
inv = [pow(i, m - 2, m) for i in fact]
f = lambda i: fact[i[0] + i[1]] * inv[i[0]] * inv[i[1]] % m
dp = [0] * (n + 1)
p = [[int(i) - 1 for i in input().split(" ")] for j in range(n)]
p = sorted(p + [[h - 1, w - 1]])
for i in range(n + 1):
    h1, w1 = p[i]
    tot = f([h1, w1])
    for j in range(i):
        if p[j][1] > w1:
            continue
        tot = (tot - dp[j] * f([h1 - p[j][0], w1 - p[j][1]]) % m) % m
    dp[i] = tot
print(dp[-1])

Fixed submission:
import sys
h, w, n = [int(i) for i in sys.stdin.readline().split()]
m = 1000000007
fact = [1, 1]
for i in range(2, 200002):
    fact.append(fact[-1] * i % m)
inv = [pow(i, m - 2, m) for i in fact]
f = lambda i: fact[i[0] + i[1]] * inv[i[0]] * inv[i[1]] % m
dp = [0] * (n + 1)
p = [[int(i) - 1 for i in sys.stdin.readline().split()] for j in range(n)]
p = sorted(p + [[h - 1, w - 1]])
for i in range(n + 1):
    h1, w1 = p[i]
    tot = f([h1, w1])
    for j in range(i):
        if p[j][1] > w1:
            continue
        tot = (tot - dp[j] * f([h1 - p[j][0], w1 - p[j][1]]) % m) % m
    dp[i] = tot
print(dp[-1])