/**
 * Code by Patrick Sava
 * "Spiru Haret" National College of Bucharest
 **/

# include "fstream"
# include "cstring"
# include "vector"
# include "queue"
# include "bitset"
# include "algorithm"
# include "map"
# include "unordered_map"
# include "deque"
# include "string"
# include "iomanip"
# include "cmath"
# include "stack"
# include "cassert"

const char IN [ ] =  "padure2.in" ;
const char OUT [ ] = "padure2.out" ;
const int MAX = 1014 ;
const int MOD = 2000003 ;

# define pb push_back
# define mp make_pair
# define FORN( a , b , c ) for ( int a = b ; a <= c ; ++ a )
# define FORNBACK( a , b , c ) for ( int a = b ; a >= c ; -- a )

using namespace std ;

ifstream cin ( IN ) ;
ofstream cout ( OUT ) ;

int dp [ MAX ] ;
pair < int , int > points [ MAX ] ;
int fact [ MOD ] ;

int put ( int x , int y ) {
    int ret = 1 ;
    for ( ; y ; y >>= 1 ) {
        if ( y & 1 ) {
            ret = 1LL * ret * x % MOD ;
        }
        x = 1LL * x * x % MOD ;
    }
    return ret ;
}

int comb ( int x , int y ) {
    if ( x == y or y == 0 ) {
        return 1 ;
    }
    int aux1 = put ( fact [y] , MOD - 2 ) ;
    int aux2 = put ( fact [x - y], MOD - 2 ) ;
    int aux3 = 1LL * aux1 * aux2 % MOD ;
    return 1LL * fact [ x ] * aux3 % MOD ;
}

int main()
{
    fact [ 0 ] = 1 ;
    int n , m ;
    cin >> n >> m ;
    int lim = n + m ;
    FORN ( i , 1 , lim ) {
        fact [ i ] = 1LL * fact [ i - 1 ] * i % MOD ;
    }
    int k ;
    cin >> k ;
    FORN ( i , 1 , k ) {
        int x , y ;
        cin >> x >> y ;
        points [ i ] = mp ( x , y ) ;
    }
    sort ( points + 1 , points + k + 1 ) ;
    FORN ( i , 1 , k ) {
        dp [ i ] = comb ( points [ i ].first + points [ i ].second - 2 , points [ i ].first - 1 )  ;
        FORNBACK ( j , i - 1 , 1 ) {
            if ( points [ j ].second <= points [ i ].second ) {
                dp [ i ] -= dp [ j ] ;
                if ( dp [ i ] < 0 ) {
                    dp [ i ] += MOD ;
                }
            }
        }
    }
    int total = comb ( n + m - 2 , m - 1 ) ;
    FORN ( i , 1 , k ) {
        int x = n - points [ i ].first + 1 ;
        int y = m - points [ i ].second + 1 ;
        int aux = comb ( x + y - 2 , y - 1 ) ;
        int prod = 1LL * aux * dp [ i ] % MOD ;
        total -= prod ;
        if ( total < 0 ) {
            total += MOD ;
        }
    }
    cout << total << '\n' ;
    return 0;
}