测例3和4WA了，麻烦各位佬帮看一眼代码哪有问题orz

#include<stdio.h>

int main()
{
	long long dp[21][21]={1};int bar[21][21]={},m,n,p,q,i,j;
	scanf("%d %d %d %d",&m,&n,&p,&q);
	bar[p][q]=1;
	bar[p-2][q-1]=1;bar[p-2][q+1]=1;
	bar[p-1][q-2]=1;bar[p-1][q+2]=1;
	bar[p+1][q-2]=1;bar[p+1][q+2]=1;
	bar[p+2][q-1]=1;bar[p+2][q+1]=1;
	for(i=0;i<=m;i++)
    {
        if(bar[i][0]==1) 
        {
            dp[i][0]=0;
            break;
        }
        else dp[i][0]=1;
    }
    for(j=0;j<=n;j++)
    {
        if(bar[0][j]==1) 
        {
            dp[0][j]=0;
            break;
        }
        else dp[0][j]=1;
    }
	for(i=1;i<=m;i++)
		for(j=1;j<=n;j++)
			if(bar[i][j]==0) dp[i][j]=dp[i-1][j]+dp[i][j-1];
	printf("%lld",dp[m][n]);
	return 0;
}