#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repr(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, m, n) for (int i = (m); i < (n); ++i)
#define FORR(i, m, n) for (int i = (m); i >= (n); --i)
#define equals(a, b) (fabs((a) - (b)) < EPS)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
const ll mod = 1000000007;
//const ll mod = 998244353;
const int inf = 1e9 + 10;
const ll INF = 1e18;
const ld EPS = 1e-10;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }



int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(25);

  ld n, m, d;
  cin >> n >> m >> d;

  ld ans = (n - d) * 2 * (m - 1) / n / n;
  if (d == 0) ans /= 2;
  cout << ans << '\n';


  

  
  return 0;
}
#include<iostream>
using namespace std;
int main(){
	int a,b,c;
	cin>>a>>b>>c;
	if(a==b&&b!=c||a==c&&b!=c||b==c&&a!=b){
		cout<<"Yes";
	}else{
		cout<<"No";
	}
	return 0;
}