/*之前样例输出一直是19，原来忘了边界点如果他的前一个是马致点，后来的都不能走了*/
/*
作者:桦清_L
*/
#include <iostream>
using namespace std;
#define mm 21int dp[mm][mm];
int main()
{
int n,m,x,y;
cin>>n>>m>>x>>y;
for(int i=0;i<=n;i++)
for(int j=0;j<=m;j++) dp[i][j]=1;
dp[x][y] = 0;
dp[x+2][y+1] = 0;
dp[x+1][y+2] = 0;
if(x>=1)dp[x-1][y+2] = 0;
if(x>=2)dp[x-2][y+1] = 0;
if(x>=2&&y>=1)dp[x-2][y-1] = 0;
if(x>=1&&y>=2)dp[x-1][y-2] = 0;
if(y>=2)dp[x+1][y-2] = 0;
if(y>=1)dp[x+2][y-1] = 0;
for(int i=0;i<=n;i++)
for(int j=0;j<=m;j++)
{
if(!dp[i][j]||(i==0&&j==0)) continue;
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][j-1]+dp[i-1][j];
}
cout<<dp[n][m]<<endl;
return 0;
}
