#include <bits/stdc++.h>
using namespace std;
const int N = 1005;
double a[N][N];
double f[N][N];
int n, m;
int x, y;
void print() {
  for (int i = 1; i <= m; ++i) {
    for (int j = 1; j <= m; ++j) printf("%.4lf ", a[i][j]);
    puts("");
  }
}
void gauss() {
  for (int i = 1; i <= m; ++i) {
    double tmp = a[i][i];
    a[i][i] /= tmp, a[i][i + 1] /= tmp;
    if (i < m) a[i][m + 1] /= tmp;
    double t = a[i + 1][i];
    int d[3] = {i, i + 1, m + 1};
    for (int j = 0; j < 3; ++j) {
      a[i + 1][d[j]] -= t * a[i][d[j]];
    }
  }
  for (int i = m - 1; i >= 1; --i) {
    a[i][m + 1] -= a[i][i + 1] * a[i + 1][m + 1];
    a[i][i + 1] = 0;
  }
}
int main() {
  scanf("%d%d%d%d", &n, &m, &x, &y);
  if (m == 1)
    printf("%.4lf\n", (n - x) * 2.0);
  else {
    for (int i = n - 1; i >= x; --i) {
      a[1][1] = -2 / 3.0, a[1][2] = 1 / 3.0,
      a[1][m + 1] = -1 / 3.0 * f[i + 1][1] - 1;
      a[m][m] = -2 / 3.0, a[m][m - 1] = 1 / 3.0,
      a[m][m + 1] = -1 / 3.0 * f[i + 1][m] - 1;
      for (int j = 2; j < m; ++j) {
        a[j][j] = -3.0 / 4, a[j][j - 1] = 1.0 / 4, a[j][j + 1] = 1.0 / 4;
        a[j][m + 1] = -f[i + 1][j] / 4.0 - 1;
      }
      gauss();
      for (int j = 1; j <= m; ++j) f[i][j] = a[j][m + 1];
    }
    printf("%.4lf\n", f[x][y]);
  }
  return 0;
}
