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

using ll = long long;
//#define int ll
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
using pii = pair<int, int>;
using vi = vector<int>;
#define fi first
#define se second
#define pb push_back

const int N = 2222;

double p;
double dp[N][N];
double f(int n, int m)
{
    if (n > m) swap(n, m);
    if (dp[n][m] > -0.1)
        return dp[n][m];
    if (n==1 && m==1) return 0;

    if (n == 1) return f(n, m-1)+p/4;

    double a = f(n, m-1);
    double b = f(n-1, m);

    if (a > b) swap(a, b);
    double h = b-a;

    double ans = 0;

    ans += p/2 - (p-h)*max<double>(0, (1-h/p))/2;

    return dp[n][m] = ans/2+a;
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int n, m;
    cin>>n>>m>>p;
    for (int i=1; i<=n; i++)
        for (int j=1; j<=m; j++)
            dp[i][j] = -1;

    cout<<fixed<<setprecision(10);
    cout<<f(n, m)<<"\n";
}