```cpp
#include <bits/stdc++.h>
using namespace std;
int a,b,n,x,y;
int f[2000][2000];
int main(){
cin>>a>>b>>n;
for(int i=1;i<=a;i++) for(int j=1;j<=b;j++) f[i][j]=1;
for(int i=1;i<=n;i++){
cin>>x>>y;
f[x][y]=0;
}
for(int i=2;i<=a;i++) for(int j=2;j<=b;j++) if(f[i][j]!=0) f[i][j]=f[i-1][j]+f[i][j-1];
/*for(int i=1;i<=a;i++){
for(int j=1;j<=b;j++) cout<<f[i][j]<<' ';
cout<<endl;
}*/
cout<<f[a][b];
return 0;
}
```
by tanglejin @ 2022-08-23 12:59:55