求助！万分感谢！

#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
long long cb[40][40],kp[40][40];
int main(){
	long long bx,by,hx,hy;
	cin>>bx>>by>>hx>>hy;
	int ci[8][3]={{-2,-1},{-1,-2},{1,-2},{2,-1},{-2,1},{-1,2},{1,2},{2,1}};
	for(long long i=0;i<8;i++){
		if(hx+ci[i][0]<=40 && hy+ci[i][1]<=40) //防越界 
			kp[hx+ci[i][0]][hy+ci[i][1]]=1;
	}
	kp[hx][hy]=1;
	if(kp[0][0]==1)
		cb[0][0]=1;
	else
		cb[0][0]=0;
	for(long long i=1;i<=bx;i++){
		cb[i][0]=1;
	}
	for(long long i=1;i<=by;i++){
		cb[0][i]=1;
	}
	for(long long i=1;i<=bx;i++){
		for(long long j=1;j<=by;j++){
			if(kp[i][j]==0)
				cb[i][j]=cb[i][j-1]+cb[i-1][j];
		}
	}
	cout<<cb[bx][by];
	return 0;
}