Problem: Alex enjoys performing magic tricks. He has a trick that requires a deck of n cards. He has m identical decks of n different cards each, which have been mixed together. When Alex wishes to perform the trick, he grabs n cards at random and performs the trick with those. The resulting deck looks like a normal deck, but may have duplicates of some cards.

The trick itself is performed as follows: first Alex allows you to choose a random card from the deck. You memorize the card and put it back in the deck. Then Alex shuffles the deck, and pulls out a card. If the card matches the one you memorized, the trick is successful.

You don't think Alex is a very good magician, and that he just pulls a card randomly from the deck. Determine the probability of the trick being successful if this is the case.

Input

First line of the input consists of two integers n and m (1 ≤ n, m ≤ 1000), separated by space — number of cards in each deck, and number of decks.

Output

On the only line of the output print one floating point number – probability of Alex successfully performing the trick. Relative or absolute error of your answer should not be higher than 10 - 6.

Examples

Input

2 2


Output

0.6666666666666666


Input

4 4


Output

0.4000000000000000


Input

1 2


Output

1.0000000000000000

Note

In the first sample, with probability <image> Alex will perform the trick with two cards with the same value from two different decks. In this case the trick is guaranteed to succeed.

With the remaining <image> probability he took two different cards, and the probability of pulling off the trick is <image>.

The resulting probability is <image>

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
const int oo = (int)1e9;
const double PI = 2 * acos(0.0);
const double eps = 1e-9;
double pss[1001];
double test(int n, int m, int trials) {
  double cnt = 0;
  for (int t = 0; t < (int)(trials); ++t) {
    vector<int> arr;
    for (int i = 0; i < (int)(m); ++i)
      for (int i = 0; i < (int)(n); ++i) arr.push_back(i);
    vector<int> v;
    for (int i = 0; i < (int)(n); ++i) {
      int r = rand() % (n * m - i);
      v.push_back(arr[r]);
      swap(arr[r], arr.back());
      arr.pop_back();
    }
    int r1 = rand() % ((long long)v.size());
    int r2 = rand() % ((long long)v.size());
    if (v[r1] == v[r2]) cnt++;
  }
  return cnt / trials;
}
int main() {
  ios_base::sync_with_stdio(false);
  double n, m;
  cin >> n >> m;
  double ans = (1 / n);
  if (m * (n - 1) >= (n - 2) && m >= 2) {
    ans += (m / (m * n) * (m - 1) / (m * n - 1)) * (n - 1);
  }
  cout << fixed << setprecision(10) << ans << endl;
  return 0;
}