#include <bits/stdc++.h>
using namespace std;
const int N = 1500;
double dp[N][N], mp[N][N];
int n, m;
void gauss() {
  for (int i = 1; i <= m; i++) {
    double t = dp[i + 1][i] / dp[i][i];
    int d[3] = {i, i + 1, m + 1};
    for (int j = 0; j < 3; j++) dp[i + 1][d[j]] -= t * dp[i][d[j]];
    dp[i + 1][i] = 0;
  }
  for (int i = m; i; i--) {
    dp[i - 1][m + 1] -= dp[i - 1][i] / dp[i][i] * dp[i][m + 1];
    dp[i - 1][i] = 0;
  }
}
int main() {
  ios::sync_with_stdio(false);
  int x, y;
  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--) {
      dp[1][1] = 2.0 / 3.0;
      dp[1][2] = -1.0 / 3.0;
      dp[1][m + 1] = mp[i + 1][1] / 3 + 1;
      dp[m][m] = 2.0 / 3.0;
      dp[m][m - 1] = -1.0 / 3.0;
      dp[m][m + 1] = mp[i + 1][m] / 3 + 1;
      for (int j = 2; j < m; j++) {
        dp[j][j - 1] = -1.0 / 4;
        dp[j][j] = 3.0 / 4.0;
        dp[j][j + 1] = -1.0 / 4.0;
        dp[j][m + 1] = mp[i + 1][j] / 4.0 + 1;
      }
      gauss();
      for (int j = 1; j <= m; j++) mp[i][j] = dp[j][m + 1] / dp[j][j];
    }
    printf("%.4lf\n", mp[x][y]);
  }
  return 0;
}
