#include <bits/stdc++.h>
using namespace std;
using ui = unsigned int;
using ull = unsigned long long;
using ll = long long;
#define endl '\n'
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int maxn = 2e5 + 10;
const int mod = 1000000007;
#define inl inline
#define fr(i, a, b) for (int i = a; i <= b; i++)
#define ford(i, a, b) for (int i = a; i >= b; i--)
#define forall(i, a) for (auto &i : a)

/**
   ____         ___ _____
  / ___| _   _ / _ \___ /
  \___ \| | | | | | ||_ \
   ___) | |_| | |_| |__) |
  |____/ \__, |\___/____/
         |___/
*/
istream &operator>>(istream &in, vector<int> &v)
{
    for (auto &i : v)
        in >> i;
    return in;
}
ostream &operator<<(ostream &out, vector<int> &v)
{
    for (auto &i : v)
        out << i << " ";
    return out;
}
bool _output = 0;

#define int long long
using db = double;
void solve()
{
    int r, c;
    cin >> r >> c;
    int p;
    cin >> p;
    vector<vector<db>> f(r + 2, vector<db>(c + 2, 1e13));
    f[r][c] = 0;
    for (int i = r; i >= 1; i--)
    {
        for (int j = c; j >= 1; j--)
        {
            if (r == i && c == j)
                continue;
            db x = min(f[i][j + 1], f[i + 1][j]);
            db y = max(f[i][j + 1], f[i + 1][j]);
            db z = min(1.0 * (y - x), 1.0 * p);
            db t = 1.0 * p * x + 1.0 * z * x + 1.0 * (z)*z / 2.0 + 1.0 * y * (p - z);
            f[i][j] = t / (2.0 * p);
            // if (i == 4 && j == 4)
            //     cout << x << " " << y << " " << z << " " << t << endl;
            // cout << i << " " << j << " " << f[i][j] << "\n";
        }
        // cout << endl;
    }
    cout << fixed << setprecision(6) << f[1][1] << endl;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int _ = 1;
    if (_output)
        cin >> _;
    while (_--)
        solve();
    return 0;
}