#include <bits/stdc++.h>
using namespace std;
template <class T>
void show(T a, int n) {
  for (int i = 0; i < n; ++i) cout << a[i] << ' ';
  cout << endl;
}
template <class T>
void show(T a, int r, int l) {
  for (int i = 0; i < r; ++i) show(a[i], l);
  cout << endl;
}
const int N = 128 * 2;
const int M = 5000;
const int oo = 10000 * 10000 * 10;
int main() {
  int i, j, cas = 0;
  int n, m, k;
  scanf("%d %d %d", &n, &m, &k);
  double ans = 1;
  if (m > n + k) {
    ans = 0;
  } else {
    for (i = m - k; i <= m; ++i) ans *= i;
    for (i = n + 1; i <= n + k + 1; ++i) ans /= i;
    ans = 1.0 - ans;
  }
  printf("%0.10f\n", ans);
  return 0;
}
