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;
static double m1[2000];
int main() {
  ios_base::sync_with_stdio(0);
  int n, m;
  cin >> n >> m;
  double res = 0;
  m1[0] = 1;
  for (int i = 0; i <= min(n, m); ++i) {
    m1[i] = 1;
    for (int j = 0; j < i; ++j) m1[i] *= (1. * m - j) / (n * m - j);
    for (int j = i; j < n; ++j)
      m1[i] *= 1. * ((1. * n - 1) * m - j + i) / (j - i + 1) /
               (1. * n * m - j) * (j + 1);
  }
  for (int i = 0; i <= min(n, m); ++i) res += m1[i] * i * i / n;
  cout << setprecision(9) << fixed << res << endl;
  return 0;
}