#include <iostream>
#include <algorithm>
using namespace std;
long long a[30][30];
int main(){
    long long n,m;
    cin>>n>>m;
    long long b,c;
    cin>>b>>c;
    a[0][0]=1;
    a[b][c]=-1;
    a[b-2][c+1]=-1;
    a[b-2][c-1]=-1;
    a[b-1][c-2]=-1;
    a[b+1][c-2]=-1;
    a[b+2][c-1]=-1;
    a[b+2][c+1]=-1;
    a[b+1][c+2]=-1;
    a[b-1][c+2]=-1;
    for(long long i=0;i<=n;i++){
        for(long long j=0;j<=m;j++){
            if(i==0&&j==0)continue;
            if(a[i][j]==-1)continue;
            if(a[i-1][j]==-1){
                a[i][j]=a[i][j-1];
            }
            else if(a[i][j-1]==-1){
                a[i][j]=a[i-1][j];
            }
            else{
                a[i][j]=a[i-1][j]+a[i][j-1];
            }
        }
    }
    cout<<a[n][m]<<endl;
    return 0;
}

80分 求助