#include<bits/stdc++.h>
using namespace std;
using ull=unsigned long long;
#define mod 1000000007
#define mod2 998244353 
#define PI 3.14159265
#define ll long long
#define ld long double
#define pi pair<ll,ll>
#define pb push_back
#define vi vector<ll>
#define sz size()
#define setbits(x)  __builtin_popcount(x)
#define fi first
#define se second
#define lz length()
#define all(x) (x).begin(),(x).end()
#define scf(x) scanf("%lld",&x)
#define rep(i,n) for(ll i=0;i<n;i++)
const int INF = (int)1e9;
const ll IINF=1LL<<62;
const int maxn=10000005;

//int divr[maxn];
/**/
/*void divisor()
{for(int i=2;i<sqrt(maxn);i++)
     {
          if(!divr[i])
          {
               for(int j=i*i;j<maxn;j+=i)if(!divr[j])divr[j]=i;     
          }
     }
     for(int i=1;i<maxn;i++)if(!divr[i])divr[i]=i;
}*/
 
/*const int N=1000005;
ll n;
struct line {
    long long m, c;
    long long eval(long long x) { return m * x + c; }
    long double intersectX(line l) { return (long double) (c - l.c) / (l.m - m); }
};
vector<pair<pi,ll>> rect;
deque<line> dq;
*/
ll modexpo(ll a,ll b)
{
     ll res=1LL;
     while(b>0)
     {
          if(b&1)res=(res*a)%mod;
          a=(a*a)%mod;
          b>>=1;
     }
     return res;
}
 
 
 
 
 
 
 




bool s[405][405];
bool used[405][405];
int dx[]={1,-1,0,0};
int dy[]={0,0,1,-1};
int main()
{
     ll n,m,d;
     cin>>n>>m>>d;
     ll t=(n-d);
     if(d!=0)t*=2;
     ld res=(double)(1.0*t/(1LL*n*n))*(m-1.0);
    cout<<fixed<<setprecision(10)<<res;
}


































#include <bits/stdc++.h>
#define REP(i,n) for (int i = 0; i < n; i++) 
using namespace std;

int main() {
  
  string a, b, c;
  cin >> a >> b >> c;
  
  int ai = a.size() - 1;
  int bi = b.size() - 1;
  
  
  if (a[ai] == b[0] && b[bi] == c[0]) cout << "YES" << endl;
  else cout << "NO" << endl;

}