#include <bits/stdc++.h>

#define LL long long
#define ull unsigned long long
#define F(i, j, k) for (int i = j; i <= k; ++i)
#define DF(i, j, k) for (int i = j; i >= k; --i)

using namespace std;

template <typename T> inline void read(T &n) {
    T w = 1;
    n = 0;
    char ch = getchar();
    while (!isdigit(ch) && ch != EOF) {
        if (ch == '-') w = -1;
        ch = getchar();
    }
    while (isdigit(ch) && ch != EOF) {
        n = (n << 3) + (n << 1) + (ch & 15);
        ch = getchar();
    }
    n *= w;
}

template <typename T> inline void write(T x) {
    T l = 0;
    ull y = 0;
    if (!x) { putchar(48); return; }
    if (x < 0) { x = -x; putchar('-'); }
    while (x) { y = y * 10 + x % 10; x /= 10; ++l; }
    while (l) { putchar(y % 10 + 48); y /= 10; --l; }
}

template <typename T> inline void writes(T x) {
    write(x);
    putchar(' ');
}

template <typename T> inline void writeln(T x) {
    write(x);
    puts("");
}

template <typename T> inline void checkmax(T &a, T b) { a = a > b ? a : b; }

template <typename T> inline void checkmin(T &a, T b) { a = a < b ? a : b; }

double dp[1010][1010];

int main() {
    //freopen(".in", "r", stdin);
    //freopen(".out", "w", stdout);
    int n, m, P;
    read(n); read(m); read(P);
    double p = P;
    F(i, 1, n)
        F(j, 1, m) {
            if (i == 1 && j == 1) { dp[i][j] = 0; continue; }
            if (i == 1) { dp[i][j] = dp[i][j - 1] + 0.25 * p; continue; }
            if (j == 1) { dp[i][j] = dp[i - 1][j] + 0.25 * p; continue; }
            if (dp[i - 1][j] < dp[i][j - 1]) {
                double cur = min(dp[i][j - 1] - dp[i - 1][j], p);
                dp[i][j] = 0.5 * dp[i - 1][j] + 0.5 * cur / p * (dp[i - 1][j] + 0.5 * cur) + 0.5 * (1 - cur / p) * dp[i][j - 1];
            }
            else {
                double cur = min(dp[i - 1][j] - dp[i][j - 1], p);
                dp[i][j] = 0.5 * dp[i][j - 1] + 0.5 * cur / p * (dp[i][j - 1] + 0.5 * cur) + 0.5 * (1 - cur / p) * dp[i - 1][j];
            }
        }
    cout << fixed << setprecision(10) << dp[n][m] << '\n';
    return 0;
}