#include <bits/stdc++.h>

using namespace std;
const int N = 22;
int ctrl[N][N];
int n, m;
int mx, my;

//深搜
int dfs(int x, int y) {
    //终点
    if (x == n && y == m) return 1;
    //不能走
    if (ctrl[x][y] || x > n || y > m) return 0;
    //向右 向下
    return dfs(x + 1, y) + dfs(x, y + 1);
}


//增量数组，delta
int d[8][2] = {
        {1,  2},
        {1,  -2},
        {-1, 2},
        {-1, -2},
        {2,  1},
        {2,  -1},
        {-2, 1},
        {-2, -1}};

int main() {
    //读入B点坐标和马的坐标
    cin >> n >> m >> mx >> my;
    //马的实际控制范围
    for (int i = 0; i < 8; i++) {
        int tx = mx + d[i][0], ty = my + d[i][1];
        if (tx >= 0 && tx <= n && ty >= 0 && ty <= m) ctrl[tx][ty] = 1;
    }
    //马所在的位置你也不能走，也踢你~
    ctrl[mx][my] = 1;

    //深搜
    int sum = dfs(0, 0);

    //输出
    printf("%d\n", sum);
}