#include <bits/stdc++.h>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int r, c, p;
    cin >> r >> c >> p;

    vector dp(r, vector<double>(c));
    for (int i = r - 1; i >= 0; --i) {
        for (int j = c - 1; j >= 0; --j) {
            if (i == r - 1 && j == c - 1) {
                continue;
            } else if (i == r - 1) {
                dp[i][j] = dp[i][j + 1] + p * 0.25;
            } else if (j == c - 1) {
                dp[i][j] = dp[i + 1][j] + p * 0.25;
            } else {
                double x = dp[i + 1][j], y = dp[i][j + 1];
                if (x > y) {
                    swap(x, y);
                }

                dp[i][j] += x / 2;
                double lim = min<double>(p, y - x);
                dp[i][j] += (x + lim / 2) / 2 * (lim / p);
                dp[i][j] += y / 2 * ((p - lim) / p);
            }
        }
    }

    cout << fixed << setprecision(10) << dp[0][0] << '\n';
}