#include<bits/stdc++.h>
//#include<atcoder/all>

using namespace std;
//using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007



int main(){
  
  cout << fixed << setprecision(20);
  ll a,b;
  cin >> a >> b;
  ll c = __gcd(abs(a),abs(b));
  double res = 0;
  if(c > 18){
    cout << 0.25 << "\n";
    return 0;
  }
  rep(i,20)rep(j,20){
    if(2+c*i+c*j > 18)break;
    __int128_t k = 1;
    rep(g,2+c*i+c*j)k = k*(2+c*i+c*j);
    if(k >= (ll)1e16)break;
    res += 1.0/k;
  }
  cout << res << "\n";


  return 0;
}