#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int sum = 0, nega = 1;
  char ch = getchar();
  while (ch > '9' || ch < '0') {
    if (ch == '-') nega = -1;
    ch = getchar();
  }
  while (ch <= '9' && ch >= '0') sum = sum * 10 + ch - '0', ch = getchar();
  return sum * nega;
}
int m, n, k;
double ans = 1;
int main() {
  n = read(), m = read(), k = read();
  if (k >= m) {
    puts("1.0000");
    return 0;
  } else if (m > n + k) {
    puts("0.0000");
    return 0;
  }
  for (int i = 1; i <= k + 1; i++)
    ans = ans * 1.0 / (n + i) * 1.0 * (m - k - 1 + i) * 1.0;
  printf("%.12lf\n", 1 - ans);
  return 0;
}
