image.png

public class Main{  
    static int BX ;
    static int BY ;
    static int CX ;
    static int CY ;
    static char[][] area;
    static int ans;
    
    static int[] MX = {2,1,-1,-2,-2,-1,1,2};
    static int[] MY = {1,2,2,1,-1,-2,-2,-1};
    
    static int[] px = {0,1};
    static int[] py = {1,0};
    
    static int[] MAR ;
    static int[] MAC ;
    
    static long[][] dp;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        BX = sc.nextInt();
        BY = sc.nextInt();
        CX = sc.nextInt();
        CY = sc.nextInt();
        
        MAR = new int[8];
        MAC = new int[8];
        
        area = new char[BX+1][BY+1];
        dp = new long[BX+1][BY+1];
        
        
        for (int i = 0; i < BX+1; i++) {
            for (int j = 0; j < BY+1; j++) {
                area[i][j] = 'O';
            }
        }
        
        area[CX][CY] = 'M';
        for (int i = 0; i != 8; i++) {
            if (CX+MX[i] < 0 || CX+MX[i] > BX || CY+MY[i] < 0 || CY+MY[i] >BY) {
                continue;
            }
            MAR[i] = CX + MX[i];
            MAC[i] = CY + MY[i];
            area[MAR[i]][MAC[i]] = 'M';
            
        }

        for (int i = 0; i <= BX; i++) {
            for (int j = 0; j <= BY; j++) {
                if (area[i][j] == 'M') {
                    dp[i][j] = 0;
                }else if(i == 0 && j == 0){
                    dp[i][j] = 1;
                }else if(i == 0 && j > 0){
                    dp[i][j] = dp[i][j-1];
                }else if(i > 0 && j == 0){
                    dp[i][j] = dp[i-1][j];
                }else{
                    dp[i][j] = dp[i-1][j]+dp[i][j-1];
                }
            }
        }
        System.out.println(dp[BX][BY]);     
    }
}