#include <bits/stdc++.h>
int main() {
  double ans;
  int i, n, m, k;
  while (scanf("%d%d%d", &n, &m, &k) != EOF) {
    if (k >= m)
      ans = 1;
    else if (n + k < m)
      ans = 0;
    else {
      ans = 1;
      for (i = 0; i <= k; i++) {
        ans = ans * (m - i) / (n + i + 1);
      }
      ans = 1 - ans;
    }
    printf("%.4lf\n", ans);
  }
  return 0;
}
