#include<bits/stdc++.h>
using namespace std;
using ll=long long;
template<typename T>
ostream& operator << (ostream &out,const vector<T>&x){
	if(x.empty())return out<<"[]";
	out<<'['<<x[0];
	for(int len=x.size(),i=1;i<len;i++)out<<','<<x[i];
	return out<<']';
}
template<typename T>
vector<T> ary(const T *a,int l,int r){
	return vector<T>{a+l,a+1+r};
}
template<typename T>
void debug(T x){
	cerr<<x<<'\n';
}
template<typename T,typename ...S>
void debug(T x,S ...y){
	cerr<<x<<' ',debug(y...);
}
const int N=1e2+10;
struct zj{
	double k,b;//k*f[0]+b
	zj operator + (const zj &x)const{
		return {k+x.k,b+x.b};
	}
	zj operator - (const zj &x)const{
		return {k-x.k,b-x.b};
	}
	zj operator * (const double &x)const{
		return {k*x,b*x};
	}
}f[N];
int dL,dW,G,L;
double Gp,Lp;
int main(){
	cin>>dL>>dW>>G>>L,Gp=G/100.0,Lp=L/100.0;
	f[100]={1-Gp,1/(1-Lp)};
	for(int i=99;i>=0;i--){
		f[i]=f[min(100,i+dL)]*Lp+f[min(100,i+dW)]*(1-Lp)*(1-i/100.0);
		f[i].b+=1,f[i].k+=(1-Lp)*(i/100.0)*(1-Gp);
		// debug(i,f[i].k,f[i].b);
	}
	printf("%.15lf\n",f[0].b/(1-f[0].k));
	return 0;
}