#include<iostream>
#define MAXN 100000000
using namespace std;
int hx, hy, ex, ey;
long long dp[25][25];
int horse[8][2] = {{-2, -1}, {-2, 1}, {-1, -2}, {-1, 2}, {1, -2}, {1, 2}, {2, -1}, {2, 1}};
void start() {
	for (int i = 0; i < 8; i++) {
		int tx = hx + horse[i][0];
		int ty = hy + horse[i][1];
		if (tx < 0 || ty < 0) {
			continue;
		}
		dp[tx][ty] = MAXN;
	}
	dp[hx][hy] = MAXN;
	bool f1 = true;
	bool f2 = true;
	for (int i = 0; i <= ex; i++) {
		if (dp[i][0] == MAXN) {
			f1 = false;
		}
		if (dp[0][i] == MAXN) {
			f2 = false;
		}
		if (!f1) {
			dp[0][i] = 1;
		}
		else if (!f2) {
			dp[i][0] = 1;
		}
		else {
			dp[i][0] = dp[0][i] = 1;
		}
	}
}
int main() {
	cin >> ex >> ey >> hx >> hy;
	start();
	for (int i = 1; i <= ex; i++) {
		for (int j = 1; j <= ey; j++) {
			if (dp[i - 1][j] == MAXN && dp[i][j - 1] == MAXN) {
				continue;
			} 
			else if (dp[i - 1][j] == MAXN) {
				dp[i][j] = dp[i][j - 1];
			}
			else if (dp[i][j - 1] == MAXN) {
				dp[i][j] = dp[i - 1][j];
			}
			else if (dp[i][j] == MAXN) {
				continue;
			}
			else {
				dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
			}
		}
	}
	cout << (dp[ex][ey] == MAXN ? 0 : dp[ex][ey]);
	return 0;
}