#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 50;

int X1, Y1, X2, Y2;
int dx[] = {2, 1, -1, -2, -2, -1, 1, 2}, dy[] = {1, 2, 2, 1, -1, -2, -2, -1};
ll f[N][N];
bool vis[N][N];

int main() {
    scanf("%d%d%d%d", &X1, &Y1, &X2, &Y2);
    vis[X2][Y2] = true;
    for (int i = 0; i < 8; i++) {
        int xx = X2 + dx[i], yy = Y2 + dy[i];
        if (xx >= 0 && xx <= X1 && yy >= 0 && yy <= Y1)
            vis[xx][yy] = true;
    }
    f[0][0] = 1;
    for (int i = 1; i <= X1; i++) {
        if (vis[0][i] == false)
            f[0][i] = f[0][i - 1];
        else
            f[0][i] = 0;
    }
    for (int i = 1; i <= Y1; i++) {
        if (vis[i][0] == false)
            f[i][0] = f[i - 1][0];
        else
            f[i][0] = 0;
    }
    for (int i = 1; i <= X1; i++)
        for (int j = 1; j <= Y1; j++)
            if (vis[i][j] == false)
                f[i][j] = f[i - 1][j] + f[i][j - 1];
            else
                f[i][j] = 0;
    printf("%lld\n", f[X1][Y1]);
    return 0;
}