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;
double ans, res, n, m, i, j, all, now;
double DP[1002][1002];
int main() {
  cin >> n >> m;
  DP[0][0] = 1;
  for (i = 1; i <= n; i++)
    for (j = 0; j <= min((int)i, int(m)); j++) {
      if (j >= 1)
        DP[(int)i][(int)j] =
            DP[(int)i - 1][(int)j - 1] * (m - j + 1) / (n * m - i + 1) +
            DP[(int)i - 1][(int)j] * (n * m - i + 1 - (m - j)) /
                (n * m - i + 1);
      else
        DP[(int)i][(int)j] = DP[(int)i - 1][(int)j] *
                             (n * m - i + 1 - (m - j)) / (n * m - i + 1);
    }
  for (i = 1; i <= min(n, m); i++) {
    now = DP[(int)n][(int)i] * i * i / n;
    ans += now;
  }
  printf("%.10f\n", ans);
}