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

int main() {
    int r, c;
    long double p;
    cin >> r >> c >> p;
    long double dp[r][c];
    dp[r - 1][c - 1] = 0;
    for (int i = r - 1; i >= 0; i--) {
        for (int j = c - 1; j >= 0; j--) {
            if (i == r - 1 && j == c - 1) continue;
            long double di = (i == r - 1) ? (1 << 40) : dp[i + 1][j];
            long double dj = (j == c - 1) ? (1 << 40) : dp[i][j + 1];
            long double t = min(p, max((long double)0, dj - di));
            long double ans = t * t / 2 + t * di + (p - t) * dj;

            t = min(p, max((long double)0, di - dj));
            ans += t * t / 2 + t * dj + (p - t) * di;
            dp[i][j] = ans / 2 / p;
        }
    }

    cout << setprecision(11);
    cout << dp[0][0] << endl;
}