9
 8
 6
 4
 7
 5
 2

1  2  3  4  5  6  7  8 
2  4  6  8 11 13 15 17 
3  6 10 13 16 20 23 26 
4  8 13 17 22 26 31 35 
5 11 16 22 27 33 38 44 
6 13 20 26 33 40 46 53 
7 15 23 31 38 46 54 62 
8 17 26 35 44 53 62 71 
 1  2  3  4  5  6  7 
2  4  6 10 12 14 16 
3  6 11 14 17 22 25 
4 10 14 20 24 30 34 
5 12 17 24 31 36 43 
6 14 22 30 36 44 52 
7 16 25 34 43 52 61 
 1  2  3  4  5 
2  4 10 12 14 
3 10 13 20 23 
4 12 20 24 32 
5 14 23 32 41 
 1  2  3 
2 10 12 
3 12 21 
 1  2  3  4  5  6 
2  4  6 11 13 15 
3  6 12 15 21 24 
4 11 15 22 26 33 
5 13 21 26 34 42 
6 15 24 33 42 51 
 1  2  3  4 
2  4 11 13 
3 11 14 22 
4 13 22 31 
 1 

#include <bits/stdc++.h>
using namespace std;
long long a[22][22];
int n, m;
bool x[22][22];
int f[2][8] = {2, 1, -1, -2, -2, -1, 1, 2, -1, -2, -2, -1, 1, 2, 2, 1};
bool mx(int z, int y) {
  if (z < 0 || z > y) return false;
  return true;
}
int main() {
  int x1, x2;
  cin >> n >> m >> x1 >> x2;
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= n; j++) a[i][j] = 0;
  x[x1][x2] = true;
  for (int i = 0; i < 8; i++) {
    if (!mx(x1 + f[0][i], n) || !mx(x2 + f[1][i], m)) continue;
    x[x1 + f[0][i]][x2 + f[1][i]] = true;
  }
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= m; j++) {
      if (x[i][j])
        continue;
      else if (i == 0 && j == 0)
        a[i][j] = 1;
      else if (i == 0)
        a[i][j] = a[i][j - 1];
      else if (j == 0)
        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;
}
