#include <bits/stdc++.h>
using namespace std;
#define xx first
#define yy second
#define endl "\n"
#define pb push_back
#define int long long
#define ll long long
#define lowbit(x) x & (-x)
typedef pair<int, int> pii;
#define LF(x) fixed << setprecision(x)
#define Yshanqian ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
const int N = 1e6 + 10, M = 1010, inf = 0x3f3f3f3f, mod = 1e9 + 7, P = 13331;
int n, m;
void solve()
{
    cin >> n >> m;
    double p;
    cin >> p;
    vector dp(n + 1, vector<double>(m + 1));
    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)
            {
                dp[i][j] = 1.0 * p / 4 + dp[i][j + 1];
            }
            else if (j == m)
            {
                dp[i][j] = 1.0 * p / 4 + dp[i + 1][j];
            }
            else
            {
                double b = max(dp[i + 1][j], dp[i][j + 1]), a = min(dp[i + 1][j], dp[i][j + 1]);
                if (b >= a + p)
                    dp[i][j] = a + 1.0 * p / 4;
                else
                    dp[i][j] = (p - b + a) / (2 * p) * b + a / 2 + (b - a) / (2 * p) * (a + b) / 2;
            }
        }
    }
    cout << dp[1][1] << endl;
}
signed main()
{
    Yshanqian;
    int T;
    T = 1;
    cout << LF(10);
    // cin >> T;
    for (int cases = 1; cases <= T; ++cases)
    {
        // cout<<"Case #"<<cases<<": ";
        solve();
    }
    return 0;
}