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;
int n, m;
double ans = 0, tot;
double c[1002] = {}, c2[1002];
int main() {
  cin >> n >> m;
  tot = n * m;
  c[0] = 1;
  for (int i = 0; i < (int)(n); i++) {
    for (int j = 0; j < (int)(m + 1); j++) c2[j] = 0;
    for (int j = 0; j < (int)(m + 1); j++) {
      c2[j + 1] += c[j] * (m - j) / (tot - i);
      c2[j] += c[j] * (tot - i + j - m) / (tot - i);
    }
    for (int j = 0; j < (int)(m + 1); j++) c[j] = c2[j];
  }
  for (int i = 1; i <= min(n, m); ++i) {
    ans += c[i] * i * i;
  }
  ans /= n;
  cout << setprecision(15) << fixed << ans << endl;
  return 0;
}