#include<cstdio>
#include<string.h>
using namespace std;
long long dp[22][22],x[22][22];
int a,b,n,m,i,j;
int main()
{
    scanf("%d%d%d%d",&n,&m,&a,&b);
    memset(dp,0,sizeof(dp));
    x[a][b]=1;
    x[a-2][b+1]=1;
    x[a-2][b-1]=1;
    x[a+2][b+1]=1;
    x[a+2][b-1]=1;
    x[a-1][b+2]=1;
    x[a-1][b-2]=1;
    x[a+1][b+2]=1;
    x[a+1][b-2]=1;  
    for (i=0;i<=n;++i)
    {
        dp[i][0]=1;
        for (j=1;j<=m;++j)
        {
            if (x[i][j]) dp[i][j]=0;
            else dp[i][j]=dp[i-1][j]+dp[i][j-1];
        }
    }
    printf("%lld",dp[n][m]);
    return 0;
}