#include<iostream>
#include<algorithm>
#include<cstring>
#include<map>
using namespace std;
typedef pair<int,int> PII;
typedef long long LL;

const int N = 25;
LL f[N][N];//答案比较大
int n,m;
int sx,sy;
map<PII,int> horse;//记录马能到达的地方

int main()
{
    cin >> n >> m >> sx >> sy;

    int dx [8] = {-1,-2,-2,-1,1,2,2,1};
    int dy [8] = {-2,-1,1,2,2,1,-1,-2};
    horse[{sx,sy}] = 1;//注意马的起始点也要算上
    for(int i = 0;i < 8;i++)
    {
        int a = sx + dx[i] , b = sy + dy[i];
        horse[{a,b}] = 1;
    }
    //f[i][j] 表示走到（i,j）的合法方案数
    for(int i = 1;i <= n;i++)
    {
        if(horse.count({i,0})) break;
        f[i][0] = 1;
    }
    for(int i = 1;i <= m;i++) 
    {
        if(horse.count({0,i})) break; 
        f[0][i] = 1;
    }

    for(int i = 1;i <= n;i++)
    {
        for(int j = 1;j <= m;j++)
        {
            if(horse.count({i,j})) continue;
            f[i][j] = f[i-1][j] + f[i][j-1];

        }
    }

    cout << f[n][m] << endl;

    return 0;
}