P1002

#include<bits/stdc++.h>
using namespace std;
int bx,by,mx,my,a[30][30];//a[i][j]=a[i-1][j]+a[i][j-1];
int bj(int x,int y){
	a[x][y]=2;
    a[x-1][y-2]=2;
    a[x-2][y-1]=2;
    a[x-2][y+1]=2;
    a[x-1][y+2]=2;
    a[x+1][y-2]=2;
    a[x+2][y-1]=2;
    a[x+2][y+1]=2;
    a[x+1][y+2]=2;
}
int main(){
	cin>>bx>>by>>mx>>my;
	bx++;
	by++;
	mx++;
	my++;
	a[1][1]=1;
	for(int i=2;i<=bx;i++){
		a[i][1]=1;
	}
	for(int i=2;i<=by;i++){
		a[1][i]=1;
	}
	bj(mx,my);
	for(int i=2;i<=bx;i++){
		for(int j=2;j<=by;j++){
		   if(a[i][j]==2){
			a[i][j]=0;
			continue;
		}
			a[i][j]=a[i-1][j]+a[i][j-1];
		}
	}
	cout<<a[bx][by];
}