过河卒

#include <bits/stdc++.h>
using namespace std;
int a[30][30];
int dx[]={0,0,-1};
int dy[]={0,1,0};
int k=0;
void aa(int n,int m,int x,int y,int bx,int by){
	if(bx<0 || by<0 || bx>30 || by>30) return;
	if(a[bx][by]==1) return;
	if(a[bx][by]==2){
		k++;
		return;
	}
	for(int i=1;i<=2;i++){
		int nx=bx+dx[i];
		int ny=by+dy[i];
		aa(n,m,x,y,nx,ny);
	}
}
int main(){
	int n,m,x,y;
	a[x][y]=1;//马的坐标 
	a[x-1][y+2]=1;
	a[x+1][y+2]=1; 
	a[x-2][y+1]=1;
	a[x+2][y+1]=1;
	a[x-1][y-2]=1;
	a[x+1][y-2]=1; 
	a[x-2][y-1]=1;
	a[x+2][y-1]=1;//定义马的范围 
	a[x][y]=2;
	cin>>n>>m;
	cin>>x>>y;
	aa(n,m,x,y,0,0);
	cout<<k;
	return 0;
}