#include <iostream>
using namespace std; 
long long dp[25][25];
int xx[9] = {0,1,1,2,2,-1,-1,-2,-2};
int yy[9] = {0,-2,2,1,-1,2,-2,1,-1};
bool b[25][25];
int main(){
	int x1,y1,x2,y2;
	cin >> x1 >> y1 >> x2 >> y2;
	for (int i = 0;i<=8;i++){
		if (x2+xx[i] < 0 or y2+yy[i] < 0){
			continue;
		}
		b[x2+xx[i]][y2+yy[i]] = true;
		dp[x2+xx[i]][y2+yy[i]] = 0;
	}
	for (int i = 0;i<=x1;i++){
		for (int j = 0;j<=y1;j++){
			if (b[i][j] == true)
				continue;
			else if (i == 0 and j == 0)
				dp[i][j] = 1;
			else if (i == 0)
				dp[i][j] = dp[i][j-1];
			else if (j == 0)
				dp[i][j] = dp[i-1][j];
			else
				dp[i][j] = dp[i-1][j] + dp[i][j-1];
		}
	}
	cout << dp[x1][y1];
	return 0;
}