#include <bits/stdc++.h>
//#define int long long
#define fi first
#define se second 
#define pb push_back
#define ott(i, l, r) for (int i = (l); i <= (r); i ++)
#define tto(i, l, r) for (int i = (r); i >= (l); i --)
using namespace std;
typedef double db;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
int read () {
	int x = 0; bool f = false; char c = getchar ();
	while (!isdigit (c)) f |= (c == '-'), c = getchar ();
	while (isdigit (c)) x = (x << 3) + (x << 1) + (c ^ 48), c = getchar ();
	return f ? -x : x;
}
const int N = 1100, mod = 998244353, inf = 0x3f3f3f3f;
int n, m, p; ld f[N][N];
int main () {
	n = read (), m = read (), p = read ();
	tto (i, 1, n)
		tto (j, 1, m) {
			if (i == n && j == m) f[i][j] = 0;
			else if (i == n) f[i][j] = f[i][j + 1] + p / 4.0;
			else if (j == m) f[i][j] = f[i + 1][j] + p / 4.0;
			else {
				ld a = f[i + 1][j], b = f[i][j + 1];
				if (a > b) swap (a, b);
				if (b >= a + p) f[i][j] = a + p / 4.0;
				else f[i][j] = (p - b + a) / (2.0 * p) * b + a / 2 + (b - a) / (2.0 * p) * (a + b) / 2.0;
			}
		}
		printf ("%.6Lf\n", f[1][1]);
    return 0;
}