#include<bits/stdc++.h>
using namespace std;
long long x[40][40]={};
int p[40][40]={};
int main(){
    int m,n,a,b;
    cin>>n>>m>>b>>a;
    p[b+2][a+2]=p[b+1][a]=p[b][a+1]=p[b+3][a+4]=p[b+4][a+3]=p[b+1][a+4]=p[b][a+3]=p[b+4][a+1]=p[b+3][a]=p[b][a]=1;
    x[2][2]=1;
    for(int i=2;i<=m+2;i++){
        for(int j=2;j<=n+2;j++){
            if(p[j][i]==1)x[j][i]=0;
            else x[j][i]=x[j][i-1]+x[j-1][i];
        }
    }
    cout<<x[n+2][m+2];
    return 0;
}