#include <bits/stdc++.h>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define watch(a) { cout << #a << " = " << a << endl; }
template<class T1, class T2> inline bool minimize(T1 &a, T2 b) { return b < a && (a = b, 1); }
template<class T1, class T2> inline bool maximize(T1 &a, T2 b) { return a < b && (a = b, 1); }

typedef long long ll;

int P0, Q;

map<pair<int, int>, double> memo;

double solve(int P, int depth = 0) {
  if(depth > 1e4) return 1.0f;
  if(memo.find({P, depth}) != memo.end()) return memo[{P, depth}];
  auto& ret = memo[{P, depth}];
  return ret =
  P / 200.0 + (100 - P) / 300.0
  + P / 200.0         * solve(max(0,    P-Q), depth + 1)
  + (100 - P) / 300.0 * solve(min(100,  P+Q), depth + 1);
}

int main() {

  cin >> P0 >> Q;
  printf("%.10f\n", (1 + solve(P0)) / 3);

  return 0;
}