#include<bits/stdc++.h>

using i64 = long long;
using l64 = long double;

void DAOQI() {
    i64 r, c, p;
    std::cin >> r >> c >> p;
    std::vector f(r + 1, std::vector(c + 1, l64{}));
    for (int i = r; i >= 1; i--) {
        for (int j = c; j >= 1; j--) {
            if (i == r && j == c) {
                f[i][j] = 0;
            } else if (i == r) {
                f[i][j] = 0.25 * p + f[i][j + 1];
            } else if (j == c) {
                f[i][j] = 0.25 * p + f[i + 1][j];
            } else {
                l64 a = f[i + 1][j], b = f[i][j + 1];
                if (a > b) {
                    std::swap(a, b);
                }
                if (a + p <= b) {
                    f[i][j] = 0.25 * p + a;
                } else {
                    f[i][j] = 0.5 * (a + p - b) / p * b + 0.5 * a + 0.5 * (b - a) / p * 0.5 * (a + b);
                }
            }
        }
    }
    std::cout << std::fixed << std::setprecision(10) << f[1][1] << "\n";
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int T = 1;
    //std::cin >> T;
    while (T--) DAOQI();
    return 0;
}