//hdu robot   
#include    
#include    
#include    
#include    
using namespace std;  
  
inline void RD(int &ret) {  
    char c;  
    do {  
        c = getchar();  
    } while(c < '0' || c > '9') ;  
    ret = c - '0';  
    while((c=getchar()) >= '0' && c <= '9')  
        ret = ret * 10 + ( c - '0' );  
}  
  
int n,m,l,r,w;  
double dp[2][222]; //第i步操作在j点的概率   
int main() {  
    while(scanf("%d%d%d%d",&n,&m,&l,&r) != EOF){  
        if(n == 0 && m == 0 && l == 0 && r == 0) break;  
        for(int i=0; i
#include 
#include 
#include 
using namespace std;

inline void RD(int &ret) {
    char c;
    do {
        c = getchar();
    } while(c < '0' || c > '9') ;
    ret = c - '0';
    while((c=getchar()) >= '0' && c <= '9')
        ret = ret * 10 + ( c - '0' );
}

int n,m,l,r,w;
double dp[2][222]; //第i步操作在j点的概率
int main() {
    while(scanf("%d%d%d%d",&n,&m,&l,&r) != EOF){
        if(n == 0 && m == 0 && l == 0 && r == 0) break;
        for(int i=0; i