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

#define ll long long
#define ull unsigned long long

void solve()
{
    int n, m;
    double p;
    cin >> n >> m >> p;
    vector dp(n, vector<double>(m));
    for (int i = n - 1; i >= 0; i--)
    {
        for (int j = m - 1; j >= 0; j--)
        {
            if(i == n - 1 && j == m - 1)
            {
                dp[i][j] = 0;
            }
            else if(i == n - 1)
            {
                dp[i][j] = dp[i][j + 1] + p / 4;
            }
            else if(j == m - 1)
            {
                dp[i][j] = dp[i + 1][j] + p / 4;
            }
            else
            {
                double x = dp[i + 1][j], y = dp[i][j + 1];
                if(x < y)
                    swap(x, y);
                double d = x - y;
                dp[i][j] = 1.0 / 2 * y + 1.0 / 2 * min(1.0, d / p) * (min(p, d) / 2 + y) + 1.0 / 2 * max(0.0, 1 - d / p) * x;
            }
            // cerr << "dp[" << i << "][" << j << "]=" << dp[i][j] << endl;
        }
    }
    cout << setiosflags(ios::fixed) << setprecision(10) << dp[0][0] << '\n';
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int t = 1;
    while (t--)
    {
        solve();
    }
}