过河卒太难了111

#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m,x,y,dp[25][25];
signed main(){
	cin>>n>>m>>x>>y;
	for(int i=0;i<=n;i++)
		for(int j=0;j<=m;j++){
			if(abs(i-x)+abs(j-y)==3&&max(abs(i-x),abs(j-y))==2||i==x&&j==y) dp[i][j]=0;
			else if(i==0||j==0) dp[i][j]=1;
			else dp[i][j]=dp[i-1][j]+dp[i][j-1];
		}
	cout<<dp[n][m];
	return 0;
}