#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
LL n,m,a,b,f[25][25];
bool book[25][25];
LL dfs(int x,int y)
{
    bool check=(a-2==x&&b-1==y)|(a-1==x&&b-2==y)|(x==a&&y==b);
    check|=a+2==x&&b-1==y,check|=a+1==x&&b-2==y,check|=a-2==x&&b+1==y;
    check|=a-1==x&&b+2==y,check|=a+2==x&&b+1==y,check|=a+1==x&&b+2==y;
    if(check||x>n||y>m)return 0;
    if(book[x][y])return f[x][y];
    if(x==n&&y==m)return 1;
    book[x][y]=1;
    return f[x][y]=dfs(x+1,y)+dfs(x,y+1);
}
int main()
{
    scanf("%lld%lld%lld%lld",&n,&m,&a,&b);
    printf("%lld\n",dfs(0,0));
    return 0;
}