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# include <bits/stdc++.h>
using namespace std ;
typedef long long LL ;
const int N = 22 ;
int n , m , mx , my ;
LL f [ N ] [ N ] ; //一定要开long long ，
//增量数组，
int d [ 8 ] [ 2 ] = {
{ 1 , 2 } ,
{ 1 , - 2 } ,
{ - 1 , 2 } ,
{ - 1 , - 2 } ,
{ 2 , 1 } ,
{ 2 , - 1 } ,
{ - 2 , 1 } ,
{ - 2 , - 1 } } ;
int ctrl [ N ] [ N ] ;
//搜索
LL dfs ( int x , int y ) {
//计算过，直接返回
if ( dp [ x ] [ y ] ) return dp [ x ] [ y ] ;
//走不了
if ( ctrl [ x ] [ y ] | | x > n | | y > m ) return dp [ x ] [ y ] = 0 ;
//如果是终点
if ( x = = n & & y = = m ) return dp [ x ] [ y ] = 1 ;
//如果都不是，那么需要依赖于右和下的和
return dp [ x ] [ y ] = dfs ( x , y + 1 ) + dfs ( x + 1 , y ) ;
}
int main ( ) {
cin > > n > > m > > mx > > my ;
//马的实际控制范围
for ( int i = 0 ; i < 8 ; i + + ) {
int tx = mx + d [ i ] [ 0 ] , ty = my + d [ i ] [ 1 ] ;
if ( tx > = 0 & & tx < = n & & ty > = 0 & & ty < = m ) ctrl [ tx ] [ ty ] = 1 ;
}
//马所在的位置你也不能走，也踢你~
ctrl [ mx ] [ my ] = 1 ;
//开始深搜
cout < < dfs ( 0 , 0 ) ;
return 0 ;
}
