/*
dp[i][1]=1/3*(dp[i][1]+dp[i][2]+dp[i+1][1])+1 (1)
--> dp[i][1] - 1/3*dp[i][1] - 1/3*dp[i][2] = 1/3*dp[i+1][1]+1
dp[i][j]=1/4*(dp[i][j]+dp[i][j-1]+dp[i][j+1]+dp[i+1][j])+1 (2~m-1)
--> dp[i][j] - 1/4*dp[i][j] - 1/4*dp[i][j-1] - 1/4*dp[i][j+1] = 1/4*dp[i+1][j]+1
dp[i][m]=1/3*(dp[i][m]+dp[i][m-1]+dp[i+1][m])+1 (m)
--> dp[i][m]-1/3*dp[i][m]-1/3*dp[i][m-1] = 1/3*dp[i+1][m]+1
*/
#include <bits/stdc++.h>
using namespace std;
typedef int ll;
inline ll read()
{ll s=0;bool f=0;char ch=' ';while(!isdigit(ch)){f|=(ch=='-'); ch=getchar();}while(isdigit(ch)){s=(s<<3)+(s<<1)+(ch^48); ch=getchar();}return (f)?(-s):(s);
}
#define R(x) x=read()
inline void write(ll x)
{if(x<0){putchar('-'); x=-x;}if(x<10){putchar(x+'0');    return;}write(x/10);putchar((x%10)+'0');return;
}
#define W(x) write(x),putchar(' ')
#define Wl(x) write(x),putchar('\n')
const int N=1005;
int X,Y;
double dp[N][N];
double a[N][N],b[N];
inline void Debug(int n)
{int i,j;for(i=1;i<=n;i++){for(j=1;j<=n;j++) printf("%.3lf ",a[i][j]);printf("%.3lf\n",b[i]);}
}
inline void Gauss(int n)
{int i;double Div;// Debug(n);for(i=1;i<=n;i++){double Div=a[i][i];a[i][i]/=Div; b[i]/=Div;if(i==n) break;a[i][i+1]/=Div;Div=a[i+1][i]/a[i][i];a[i+1][i]-=Div*a[i][i];a[i+1][i+1]-=Div*a[i][i+1];b[i+1]-=Div*b[i];}for(i=n-1;i>=1;i--) b[i]-=b[i+1]*a[i][i+1];
}
int main()
{int i,j,n,m;R(n); R(m); R(X); R(Y);for(i=1;i<=m;i++) dp[n][i]=0.;for(i=n-1;i>=X;i--){if(m!=1){a[1][1]=2./3.; a[1][2]=-1./3.; b[1]=1./3.*dp[i+1][1]+1.;}else{a[1][1]=1./2.; b[1]=1./2.*dp[i+1][1]+1;}for(j=2;j<m;j++){a[j][j]=3./4.; a[j][j-1]=-1./4.; a[j][j+1]=-1./4.; b[j]=1./4.*dp[i+1][j]+1.;}if(m>1){a[m][m]=2./3.; a[m][m-1]=-1./3.; b[m]=1./3.*dp[i+1][m]+1.;}Gauss(m);for(j=1;j<=m;j++) dp[i][j]=b[j];}printf("%.10lf\n",dp[X][Y]);return 0;
}
/*
input
10 10
10 4
output
0.0000000000input
10 14
5 14
output
18.0038068653input
2 1
1 1
output
2.0000000000
*/