
// Problem : A - Painting
// Contest : AtCoder - Keyence Programming Contest 2020
// URL : https://atcoder.jp/contests/keyence2020/tasks/keyence2020_a
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

//Macros

#define ll long long
#define db long double
#define pb push_back
#define eb emplace_back
#define pii pair<int,int>
#define vi vector<int>
#define vii vector<pii>
#define mi map<int,int>
#define mii map<pii,int>
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()
#define sz(x) (int)x.size()
#define mod 1000000007
#define EPS 1e-9
#define io ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define inf 1e10
#define PI acos(-1.0)
#define int long long
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define N 100005

//Solution

void solve(){
    int n,m,x;
    cin>>n>>m>>x;
    if(n < m) swap(n,m);
    cout<<(n+x-1)/n<<endl;
}

signed main(){
    io;
    //freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
    int tests;
    //cin>>tests;
    tests = 1;
    while(tests--){
        solve();
    }
    return 0;
}
#include <bits/stdc++.h>
using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)   FOR(i,0,n)
#define ALL(a)     (a).begin(),(a).end()
#define PRINT(a)   cout << (a) << endl
#define RALL(v) rbegin(v), rend(v)

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second

#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\n';

using ll = long long int;
using P = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;

template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

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 (b<a) { a=b; return 1; } return 0; }

const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;

int main(){
  double n, m, d;
  cin >> n >> m >> d;

  double ans;
  if(d==0){
    ans = (m-1)/n;
  }else{
    ans = 2*(n-d)/(n*n) * (m-1);
  } 
  printf("%0.10f\n",ans);
}

