P1002为什么WA？

#define I return
#define AK 0
#define IOI ;
#include "bits/stdc++.h"
using namespace std;
long long x[21][21];
int main(){
    int a,b,c,d;
    x[0][0]=1;
    cin>>a>>b>>c>>d;
    for(int i=0;i<=a;i++){
		for(int l=0;l<=b;l++){
			if((i==0&&l==0)||(i+1==c||i-1==c)&&(l+2==d||l-2==d)||(i+2==c||i-2==c)&&(l+1==d||l-1==d)||i==c&&l==d)continue;
			x[i][l]=x[i-1][l]+x[i][l-1];
		}
	}
	cout<<x[a][b]<<endl;
    I AK IOI
}