#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}


struct Precision{
  Precision(){
    cout<<fixed<<setprecision(12);
  }
}precision_beet;

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  using D = long double;
  D p,q;
  cin>>p>>q;

  const D EPS = 1e-10;
  using T = tuple<Int, Int, D>;
  queue<T> que;
  que.emplace(1,1,1.0);

  D ans=0;
  while(!que.empty()){
    Int v,d;D x;
    tie(v,d,x)=que.front();que.pop();
    if(x<EPS) continue;    
    if(v+d==0) ans+=x*q;
    if(0<v+d&&v+d<=n) que.emplace(v+d,d,x*q);
    if(v-d==0) ans+=x*p;
    if(0<v-d&&v-d<=n) que.emplace(v-d,-d,x*p);
  }
  
  cout<<ans<<endl;
  return 0;
}