#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <iomanip>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(int i = 0;i < n;++i)
#define LONGINF 1000000000000000000
double hoge[1100][1000] = {};
double ans = 1;
int main() {
	int a,b;
	cin >> a >> b;
	ans /= 3;
	hoge[0][a] = 1;
	hoge[0][a] /= 3;
	for (int i = 0;i < 100;i++) {
		for (int q = 0;q <= 100;++q) {
			double go_hisyo = q;
			go_hisyo /= 100;
			double dont_hisyo = 1.0 - go_hisyo;
			hoge[i + 1][max(q - b, 0)] += go_hisyo * hoge[i][q] * 1 / 2;
			ans += go_hisyo * hoge[i][q] * 1 / 2;
			hoge[i + 1][min(q + b, 100)] += dont_hisyo * hoge[i][q] * 1 / 3;
			ans += dont_hisyo * hoge[i][q] * 1 / 3;
		}
	}
	cout << fixed << setprecision(10) << ans << endl;
	return 0;
}