#include<bits/stdc++.h>
using namespace std;
const int d[8][2] = {{2,1},{1,2},{-1,2},{-2,1},{-2,-1},{-1,-2},{1,-2},{2,-1}};
bool c[25][25];
long long  f[25][25],n,m,x,y;
int main(){
    cin>>n>>m>>x>>y;
    c[x][y] = true;
    for (int i =0;i<8;i++){
          int x1=x+d[i][0];
        int y1 = y+d[i][1];
        if(x1>=0&&x1<=n&&y1>=0&&y1<=m)
            c[x1][y1]=true;
    }
    f[0][0] = 1;
    for(int i =0;i<=n;i++)
        for(int j=0;j<=m;j++){
            if(!c[i][j]){
                if(i) f[i][j] += f[i-1][j];
                if(j) f[i][j] += f[i][j-1];
            }
        }
    cout<<f[n][m];
        return 0;       
}