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 N = 1000;
double tmp[N + 1];
int main() {
  int n, m;
  cin >> n >> m;
  if (n == 1) {
    printf("%.10lf\n", 1.0);
    return 0;
  }
  if (m == 1) {
    printf("%.10lf\n", 1.0 / n);
    return 0;
  }
  tmp[0] = 1;
  for (int i = 0; i < n; i++) tmp[0] *= (n * m - m - i + .0) / (n * m - i);
  for (int i = 0; i < min(n, m); i++)
    tmp[i + 1] =
        (tmp[i] * (n - i) * (m - i) / (i + 1)) / (n * m - n - m + i + 1);
  double ans = 0;
  for (int i = 1; i <= min(n, m); i++) ans += i * i * tmp[i];
  ans /= n;
  printf("%.10lf\n", ans);
  return 0;
}