#include <iostream>
#include <stdio.h>
#include <string.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <vector>
#include <math.h>
#include <bitset>
#include <algorithm>
#include <climits>
using namespace std;
#define LL long long
#define N 510
#define mod 1000000007
#define INF 0x3f3f3f3f
#define lson root<<1
#define rson root<<1|1
int dir[8][2] = { {1,2},{1,-2},{-1,2},{-1,-2},{2,-1},{2,1},{-2,-1},{-2,1}};
int dp[N][N],vis[N][N];
int main()
{
    freopen("pj024.in","r",stdin);
    freopen("pj024.out","w",stdout);
    int n,m,x,y;
    scanf("%d %d %d %d",&n,&m,&x,&y);
    x++,y++;
    memset(vis,0,sizeof(vis));
    vis[x][y] = 1;
    for(int i=0;i<8;i++)
    {
        int xx = x+dir[i][0];
        int yy = y+dir[i][1];
        if(xx>=0 && yy>=0)
            vis[xx][yy] = 1;
    }
    memset(dp,0,sizeof(dp));
    dp[1][1] = 1;
    for(int i=1;i<25;i++)
    {
        for(int j=1;j<25;j++)
        {
            if(vis[i][j]) continue;
            if(i==1 && j==1) continue;
            dp[i][j] = dp[i][j-1] + dp[i-1][j];
        }
    }
    printf("%d\n",dp[n+1][m+1]);
    return 0;
}