#include <bits/stdc++.h>
//#include <bits/extc++.h>
//using namespace __gnu_pbds;
using namespace std;

typedef long long ll;
#define int ll
#define ln '\n'
#define rep(i, a, b) for(int i = (a); i < (b); ++i)
#define repb(i, a, b) for(int i = (a); i >= (b); --i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define fastio ios_base::sync_with_stdio(0); cin.tie(0)
//#define pb push_back
#define f first
#define s second
template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<ll> vll;
typedef long double ld;
const int S = int(2e7)+10;
const ll INF = ll(1e18)+10;
const double EPS = 1e-8;
const double PI = 3.141592653589793238;
const int magic = 330LL;
int MOD = int(1e9)+7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
template <typename T> void print(T &v) { cout << sz(v) << endl; trav(x, v) cerr << x << " "; cerr << endl; }
template <class T> int sgn(T x) { return (x > 0) - (x < 0); }

void solve() {
    int n, m, p;
    cin >> n >> m >> p;
    n++; m++;
    vector<vd> f(n, vd(m,0));
    rep(i, 1, n)
        f[i][1] = (i-1)/4.0;
    rep(i, 1, m)
        f[1][i] = (i-1)/4.0;
    rep(i, 2, n)
        rep(j, 2, m) {
            double a = min(f[i-1][j], f[i][j-1]), b = max(f[i-1][j], f[i][j-1]);
            f[i][j] = 0.5*a + 0.5*(b-a >= 1 ? a+0.5 : (b-a)*((a+b)/2) + (1-b+a)*b);
        }
    cout << fixed << setprecision(10);
    cout << f[n-1][m-1]*p << endl;
}



int32_t main(){
    fastio;
    #ifdef LOCAL
    freopen("stuff.in", "r", stdin);
    #endif
    int t=1;
    // cin >> t;
    while(t--) solve();

    return 0;
}