#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f, mod = 1000000007;
const double pi = 3.1415926535897932, eps = 1e-6;
int n, m, k;
double pre[200015], ans;
int main() {
  scanf("%d%d%d", &n, &m, &k);
  bool ok1 = n + k + 1 < 0, ok2 = m - k - 1 < 0;
  if (ok1 + ok2) {
    printf("%.12lf\n", 1.0);
    return 0;
  }
  for (int(i) = (1); (i) <= (n + m + k + 1); (i)++)
    pre[i] = pre[i - 1] + log(i);
  ans = pre[m] + pre[n] - pre[n + k + 1] - pre[m - k - 1];
  printf("%.12lf\n", 1.0 - min(exp(ans), 1.0));
  return 0;
}
