#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

const int poyo = 12345;

int p,q;
double po[101][poyo];
const double half = 1.0/2.0;
const double onethird = 1.0/3.0;
const double twothird = 2.0/3.0;

double dfs(int x,int t){
  if(t==0)return 0.5; // tekitou
  if(po[x][t]!=-1)return po[x][t];
  double his = (double)x/100.0;
  // if(t==poyo-1)his=0.0;
  return po[x][t] = his*half*(1.0 + dfs(max(0,x-q),t-1)) + (1.0-his)*onethird*(1.0 + 1.0*dfs(min(100,x+q),t-1));
}

int main(){
  REP(i,101)REP(j,poyo)po[i][j]=-1;
  scanf("%d%d",&p,&q);
  printf("%.9lf\n",dfs(p,poyo-1)*onethird + onethird);
  return 0;
}