dp做

//https://www.luogu.com.cn/problem/P1002#ide

#include <bits/stdc++.h>
using namespace std;
int dx[8] = {-2, -1, 1, 2, 2, 1, -1, -2};
int dy[8] = {1, 2, 2, 1, -1, -2, -2, -1};
bool b[25][25];
long long dp[25][25];
int main() {
	int n, m, nn, mm;
	cin >> n >> m >> nn >> mm;
	b[nn][mm] = true;
	for (int i = 0; i < 8; i++) {
		int nx = nn + dx[i];
		int ny = mm + dy[i];
		if(nx<0||nx>n||ny<0||ny>m)continue;
		b[nx][ny] = true;
	}
	dp[0][0] = 1;
	for (int i = 0; i <= n; i++) {
		for (int j = 0; j <= m; j++) {
			if (b[i][j]) continue;
			if (i > 0)dp[i][j] += dp[i - 1][j];
			if (j > 0)dp[i][j] += dp[i][j - 1];
		}
	}
	cout << dp[n][m];
	return 0;
}