#include <bits/stdc++.h>
using namespace std;
int n, m, k, x[15], y[15];
inline int cmmdc(int x, int y) {
  while (y > 0) {
    int r = x % y;
    x = y;
    y = r;
  }
  return x;
}
int main() {
  scanf("%d%d%d", &n, &m, &k);
  if (n == m && n == 0)
    printf("1");
  else if ((n == 0 && k == 0) || (n + k < m))
    printf("0");
  else {
    for (int i = 0; i <= k; ++i) x[i] = m - i;
    for (int i = 0; i <= k; ++i) y[i] = n + i + 1;
    for (int i = 0; i <= k; ++i) {
      for (int j = 0; j <= k; ++j) {
        if (y[i] > 1) {
          int cm = cmmdc(x[i], y[i]);
          x[i] = x[i] / cm;
          y[i] = y[i] / cm;
        }
      }
    }
    double Prod = 1.0, ok = 0;
    for (int i = 0; i <= k; ++i) {
      Prod = Prod * (double)x[i];
      if (ok == 0) {
        ok = 1;
        for (int j = 0; j <= k; ++j) Prod = Prod / (double)y[j];
      }
    }
    printf("%f", 1.0 - Prod);
  }
  return 0;
}
