#include <bits/stdc++.h>

#define stirng string
#define vvi vector<vector<int>>
#define vi vector<int>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;

const int INF = 1e9 + 7;

int main() {
  double a, b;
  cin >> a >> b;
  printf("%f\n", (a * b) / (a + b));
  return 0;
}
