#include <bits/stdc++.h>
using namespace std;
int n, m, k;
double dp[50][500000], ans;
int f;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> m >> k;
  dp[0][k] = 1;
  if (n - m > 500)
    f = 300;
  else
    f = 900;
  if (n + k < m) {
    cout << 0;
    return 0;
  }
  for (int i = 1; i <= n + m; i++)
    for (int j = 0; j <= min(n + m + k, f); j++) {
      int t = i % 2;
      double x = dp[t ^ 1][j - 1] * (2 * n - i - j + k + 2);
      double y = dp[t ^ 1][j + 1] * (2 * m - i + j - k + 2);
      if (x < 0) x = 0;
      if (y < 0 || j + 1 == f) y = 0;
      dp[t][j] = (x + y) / (2 * (n + m - i + 1));
      if (j == f) ans += dp[t][j];
    }
  for (int i = 0; i <= min(n + m + k, f); i++) ans += dp[(n + m) % 2][i];
  cout << ans;
}
