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 bool testing = false;
void program() {
  double n, m;
  cin >> n >> m;
  if (n == 1 && m == 1)
    cout << 1;
  else
    cout << std::setprecision(17)
         << ((m - 1.0) / (m * n - 1.0)) * ((n - 1.0) / n) + 1.0 / n;
}
int main() {
  if (!testing) {
    program();
    return 0;
  }
  FILE* fin = NULL;
  fin = fopen("in.txt", "w+");
  fprintf(fin, "1 1\n");
  fclose(fin);
  freopen("in.txt", "r", stdin);
  printf("test case(1) => expected : \n");
  printf("0.6666666666666666\n");
  printf("test case(1) => founded  : \n");
  program();
  fin = fopen("in.txt", "w+");
  fprintf(fin, "4 4\n");
  fclose(fin);
  freopen("in.txt", "r", stdin);
  printf("test case(2) => expected : \n");
  printf("0.4000000000000000\n");
  printf("test case(2) => founded  : \n");
  program();
  fin = fopen("in.txt", "w+");
  fprintf(fin, "1 2\n");
  fclose(fin);
  freopen("in.txt", "r", stdin);
  printf("test case(3) => expected : \n");
  printf("1.0000000000000000\n");
  printf("test case(3) => founded  : \n");
  program();
  return 0;
}