#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pdd pair<double, double>
#define F first
#define S second
using namespace std;

int n, m;
double p;
double dp[1005][1005];

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin >> n >> m >> p;
    for (int i = n; i >= 1; i--)
        for (int j = m; j >= 1; j--)
        {
            if (i == n && j == m)
                dp[i][j] = 0;
            else if (i == n) // move right
                dp[i][j] = dp[i][j + 1] + 0.5 * p / 2.0;
            else if (j == m) // move down
                dp[i][j] = dp[i + 1][j] + 0.5 * p / 2.0;
            else 
            {
                // arrow right
                double R = dp[i][j + 1], D = dp[i + 1][j];
                for (int t = 1; t <= 2; t++)
                {
                    if (R <= D)
                        dp[i][j] += 0.5 * R;
                    else 
                    {
                        double diff = R - D;
                        if (diff >= p)
                            dp[i][j] += 0.5 * (p / 2.0 + D);
                        else 
                            dp[i][j] += 0.5 * (diff / p) * (diff / 2.0 + D) + 0.5 * (1 - diff / p) * R;
                        // (x / p) * (x / 2.0 + D) + (1 - x / p) * R
                    }
                    swap(R, D);
                }
            }
        }
    cout << fixed << setprecision(10) << dp[1][1] << '\n';
}