https://www.luogu.com.cn/record/76591006

#include <bits/stdc++.h>

using namespace std;

long long a[30][30];
short x[18] = {1, 2, 2, 1, -1, -2, -2, -1, 0}, y[18] = {-2, -1, 1, 2, 2, 1, -1, -2, 0};
bool g[30][30];

int main(){
	int n, m;
	cin >> n >> m;
	
	int nx, ny;
	cin >> nx >> ny;
	
	for (int i = 0; i <= 8; i++){
		g[nx+x[i]][ny+y[i]] = 1;
	}
	
	for (int i = 1; i <= n; i++){
		for (int j = 1; j <= m; j++){
			if (g[i][j] == 0){
				a[i][j] = a[i-1][j]+a[i][j-1];
			}else{
				a[i][j] = 0;
			}
			a[1][1] = 1;
			//printf("a[%d][%d] = a[%d][%d](%lld) + a[%d][%d](%lld) = %lld\n", i, j, i-1, j, a[i-1][j], i, j-1, a[i][j-1], a[i][j]);
		}
	}
	
	cout << a[n][m];
	
	return 0;
}