#include <bits/stdc++.h>
using namespace std;
const int MAXN = 60;
const int MAXM = 200010;
const int MAXQ = 100010;
const double EPS = 1e-8;
const double DINF = 1e30;
const int IINF = ~0U >> 3;
const long long LINF = 1LL << 61;
void debug() { cout << "error_here" << endl; }
int n, m, k;
double ans;
void init() {
  scanf("%d%d%d", &n, &m, &k);
  if (n + k < m) {
    puts("0");
    exit(0);
  }
  ans = 1;
  for (int i = 0; i <= k; ++i) ans *= (double)(m - i) / (n + 1 + i);
  printf("%.5f\n", 1 - ans);
}
int main() {
  init();
  return 0;
}
