#include <bits/stdc++.h>
using namespace std;

#define _p(...) (void)printf(__VA_ARGS__)
#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define ALL(x) (x).begin(), (x).end()
#define BIT(n) (1LL<<(n))
#define SZ(x) ((int)(x).size())
#define fst first
#define snd second
using ll=long long;using pii=pair<int,int>;using vb=vector<bool>;
using vi=vector<int>;using vvi=vector<vi>;using vvvi=vector<vvi>;
using vl=vector<ll>;using vvl=vector<vl>;using vvvl=vector<vvl>;
using vd=vector<double>;using vvd=vector<vd>;using vvvd=vector<vvd>;
using vpii=vector<pii>;using vvpii=vector<vpii>;using vvvpii=vector<vvpii>;

using T = double;

void Main() {
  int p0, q;
  cin >> p0 >> q;

  int N = 200;
  vector<vector<T>> dp(N+1, vector<T>(101));
  dp[0][p0] = 1./3;

  T w = 1./3, l = 1./3;

  rep(i, N) rep(pi, 101) {
    T p = pi /100.;
    T p2 = p/2;
    T p3 = (1-p)/3;
    T d = dp[i][pi];
    w += d * p2 + d * p3;
    l += d * p3;
    dp[i+1][max(0, pi - q)] += d * p2;
    dp[i+1][min(100, pi + q)] += d * p3;
  }
  //rep(ii,SZ(dp)) { cout << "dp["<<ii<<"]:"; rep(jj, SZ(dp[ii])) cout << ' ' << dp[ii][jj]; cout << endl; }
  cout << fixed << setprecision(10) << (w / (w+l)) << endl;
}
int main() { cin.tie(0); ios::sync_with_stdio(false); Main(); return 0; }