#include <iostream>
#include <set>
#include <algorithm>
#include <vector>

#define MAX_LINE_LENGTH 1000000

using namespace std;

int N, M;
set <pair<int, int>> mush;
vector<int> first_line;
vector<int> second_line;

bool isCellAMushroom(int i, int j)
{
	return mush.find(make_pair(i, j)) != mush.end();
}

int main()
{
	freopen("padure2.in", "r", stdin);
	freopen("padure2.out", "w", stdout);

	cin >> N >> M;

	int K; cin >> K;
	for (int i = 0; i < K; i++)
	{
		int x, y;
		cin >> x >> y;
		mush.insert(make_pair(x - 1, y - 1));
	}

	first_line.resize(MAX_LINE_LENGTH);
	second_line.resize(MAX_LINE_LENGTH);

	for (int i = 0; i < N; i++)
	{
		if (isCellAMushroom(0, i))
		{
			first_line[i] = 0;
		}
		else
		{
			first_line[i] = 1;
		}
	}


	for (int i = 1; i < M; i++)
	{
		for (int j = 0; j < N; j++)
		{
			if (isCellAMushroom(i, j))
			{
				second_line[j] = 0;
			}
			else
			{
				second_line[j] = first_line[j];
				if (j != 0)
				{
					second_line[j] += second_line[j - 1];
				}
			}
		}

		first_line = second_line;
	}

	cout << second_line[N - 1] << '\n';

	return 0;
}