#include<stdio.h>
#include<math.h>
#include<stdlib.h>
using namespace std;
long long int dp[50][50];
int bx,by,mx,my;
int walk(int a,int b)
{
int i,j;
if(a==bx&&b==by)return 1;
if(a>bx||b>by)return 0;
for(int i=a;i<=bx;i++){
for(int j=b;j<=by;j++)
if(dp[i][j]!=-1){
if(i==0&&j==0)dp[i][j]=1;
else if(i==0)dp[i][j]+=dp[i][j-1];
else if(j==0)dp[i][j]+=dp[i-1][j];
else dp[i][j]=dp[i-1][j]+dp[i][j-1];
}else{
dp[i][j]=0;
}
}
return dp[bx][by];
}
int main()
{
scanf("%d %d %d %d",&bx,&by,&mx,&my);
for(int i=0;i<=bx;i++)
for(int j=0;j<=by;j++)
{
if((abs(i-mx)==2)&&(abs(j-my)==1))dp[i][j]=-1;
else if((abs(i-mx)==1)&&(abs(j-my)==2))dp[i][j]=-1;
else if(i==mx&&j==my)dp[i][j]=-1;
else dp[i][j]=0;
}
int ret=walk(0,0);
if(ret==-1)ret=0;
printf("%lld",ret);
}