WA$3,4$求大佬

#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long x,y,n,m,dp[25][25];
    cin>>n>>m>>x>>y;
    dp[x][y]=-1;
    dp[x+2][y+1]=-1;
	dp[x+1][y+2]=-1;
	dp[x-1][y+2]=-1;
	dp[x-2][y+1]=-1;
    dp[x-2][y-1]=-1;
	dp[x-1][y-2]=-1;
	dp[x+1][y-2]=-1;
	dp[x+2][y-1]=-1;
	for(int i=0;i<=n&&dp[i][0]!=-1;i++)dp[i][0]=1;
	for(int i=0;i<=m&&dp[0][i]!=-1;i++)dp[0][i]=1;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
			if(dp[i][j]!=-1)
				dp[i][j]=max(dp[i-1][j],0ll)+max(dp[i][j-1],0ll);
	cout<<max(dp[n][m],0ll);
	return 0;
}