#include<bits/stdc++.h>
#define LL long long
using namespace std;
const int N = 1e3;
struct node{
    int x,y;

    bool operator<(const node& other) const {
        if (x < other.x) {
            return true;
        } else if (x == other.x && y < other.y) {
            return true;
        }
        return false;
    }
};
set <node>s;
int n,m,t,dp[N][N];
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(nullptr);
	cin >> n >> m >> t;
	while(t--){
		int d,f;
		cin >> d >> f;
		node a;
		a.x = d;
		a.y = f;
		s.insert(a);
	}
	for(int i = 1;i <= n;++i){
		if(s.find({1,i}) == s.end()){
			dp[1][i] = 1;
		}
	}
	for(int i = 1;i <= m;++i){
		if(s.find({i,1}) == s.end()){
			dp[i][1] = 1;
		}
	}
	for(int i = 1;i <= n;i++){
		for(int j = 1;j <= m;j++){
			if(i == 1 || j == 1){
				continue;
			}
			if(s.find({i,j}) != s.end()){
				continue;
			}else{
				dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
			}
		}
	}
	cout << dp[n][m];
	return 0;
}