#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

int main() {
    int p, q;
    cin >> p >> q;
    double ans = 1.0/3;
    array<double, 101> v{}, v2{};
    v[p] = 1.0/3;
    for (int i = 0; i < 100; ++i) {
        fill(v2.begin(),v2.end(), 0.0);
        for (int j = 0; j <= 100; ++j) {
            v2[max(0, j-q)] += v[j]*j/200;
            ans += v[j]*j/200;
            v2[min(100, j+q)] += v[j]*(100-j)/300;
            ans += v[j]*(100-j)/300;
        }
        v = v2;
    }
    printf("%.10lf\n", ans);
    return 0;
}