#include <stdio.h>
#include <stdlib.h>




int main()
{
    FILE *f = fopen("padure2.in","r");
    FILE *g = fopen("padure2.out","w");

    int n,m,i,j,k;
    fscanf(f,"%i%i",&n,&m);
    int**a,**c;
    a = (int**)malloc((n+1)*sizeof(int*));
    c = (int**)malloc((n+1)*sizeof(int*));

    for(i=0;i<=n;i++)
    {
        a[i] = (int*)calloc((m+1),sizeof(int));
        c[i] = (int*)calloc((m+1),sizeof(int));
    }
    fscanf(f,"%i",&k);
    while(k--)
    {
        fscanf(f,"%i%i",&i,&j);
        a[i][j] = 1;
    }

    for(i=2;i<=n;i++) c[i][1] = 1;
    for(i=2;i<=m;i++) c[1][i] = 1;

    for(j=2;j<=n;j++)
    {
        for(i=2;i<=m;i++)
        {
            if(a[i][j]==1)
            {
                c[i][j] = 0;
            }
            else
            {
                c[i][j] = c[i-1][j] + c[i][j-1];
            }
        }
    }

    fprintf(g,"%i\n",c[n][m]);



    return 0;
}