40pts求条

#include<bits/stdc++.h>
#define int /*unsigned */long long
using namespace std;
int n,m,qx=1,qy=1,hx,hy,s;
int a[30][30],dx[]={1,0},dy[]={0,1};
void dg(int x,int y){
	if(x==n&&y==m)
		s++;
	else{
		for(int i=0;i<2;i++){
			int tx=x+dx[i],ty=y+dy[i];
			if(a[tx][ty]!=-1&&!(tx<1||tx>n||ty<1||ty>m))
				dg(tx,ty);
		}
	}
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	cin>>n>>m;
	n++;
	m++;
	cin>>hx>>hy;
	hx++;
	hy++;
	a[hx][hy]=-1;
	a[hx-2][hy-1]=-1;
	a[hx-1][hy-2]=-1;
	a[hx+1][hy-2]=-1;
	a[hx+2][hy-1]=-1;
	a[hx+2][hy+1]=-1;
	a[hx+1][hy+2]=-1;
	a[hx-1][hy+2]=-1;
	a[hx-2][hy+1]=-1;
	dg(qx,qy);
	cout<<s;
	return 0;}