#include <iostream>
#include <cstring>
#include <bits/stdc++.h>
using namespace std;
int i,j;
const int maxn=20+5;
bool judge[maxn][maxn];
long long go[maxn][maxn]={1};
int main(){
    memset(go,0,sizeof(go));
    memset(judge,0,sizeof(judge));
    int n,m,a,b;
    cin>>n>>m>>a>>b;
    judge[a][b]=1;
    judge[a+2][b+1]=1;
    judge[a+2][b-1]=1;
    judge[a+1][b+2]=1;
    judge[a+1][b-2]=1;
    judge[a-2][b+1]=1;
    judge[a-2][b-1]=1;
    judge[a-1][b+2]=1;
    judge[a-1][b-2]=1;
    for(i=1;i<=n;i++){
        if(judge[i][0]==0) go[i][0]=1;
        else break;
    }
    for(i=1;i<=m;i++){
        if(judge[0][i]==0) go[0][i]=1;
        else break;
    }
    for(i=1;i<=n;i++){
        for(j=1;j<=m;j++){
            if(judge[i][j]==0) go[i][j]=go[i-1][j]+go[i][j-1];
        }
    }
    cout<<go[n][m]<<endl;
    return 0;
}