//动态规划
#include<iostream>
#define int long long
using namespace std;
const int N=25;
int endx,endy,hx,hy,dp[N][N],flag[N][N];
int dx[9]={0,1,2,2,1,-1,-2,-2,-1};
int dy[9]={0,2,1,-1,-2,2,1,-1,-2};
signed main(){
    cin>>endx>>endy>>hx>>hy;
    dp[0][0]=1;
    for(int i=0;i<9;i++){
        int xx=hx+dx[i],yy=hy+dy[i];
        if(xx>=0&&xx<=endx&&yy>=0&&yy<=endy){
            flag[xx][yy]=1;
        }
    }
    int id=-1;
    for(int i=1;i<=endx;i++){
        if(flag[i][0]){
            id=i;
            break;
        }
        else dp[i][0]=1;
    }
    if(id!=-1){
        for(int i=id;i<=endx;i++) flag[i][0]=1;
    }
    id=-1;
    for(int i=1;i<=endy;i++){
        if(flag[0][i]){
            id=i;
            break;
        }
        else dp[0][i]=1;
    }
    if(id!=-1){
        for(int i=id;i<=endy;i++) flag[0][i]=1;
    }
    for(int j=1;j<=endy;j++){
        for(int i=1;i<=endx;i++){
            if(flag[i][j]) continue;
            if(!flag[i-1][j]) dp[i][j]+=dp[i-1][j];
            if(!flag[i][j-1]) dp[i][j]+=dp[i][j-1];
        }
    }
    cout<<dp[endx][endy]<<endl;
    return 0;
}