#include <bits/stdc++.h>

using namespace std;
const int inf = 1e9;
const int maxn = 128;
const long double eps = 1e-9;

long double A[maxn][maxn], b[maxn];
signed main() {
    int n, k;
    long double p;
    cin >> n >> k >> p;
    const int N = 1<<n;

    const int mask = (1<<n) - 1;
    const int low = (1<<k) - 1;

    for (int i = 0; i < N; i++) {
        // E[i] = \sum _ j (p[j,i] * E[j]) + 1;
        if (__builtin_popcount(i) >= k) {
            A[i][i] = 1;
            b[i] = 0;
            continue;
        }
        A[i][i] = 1;
        for (int b: {0, 1}) {
            int j = ((i << 1) | b) & mask;
            long double prob = b ? p : 1-p;
            A[i][j] -= prob;
        }
        b[i] = 1;
    }
    for (int k = 0; k < N; k++) {
        int p = -1;
        for (int i = k; i < N; i++) {
            if (p == -1 || abs(A[i][k]) > abs(A[p][k])) {
                p = i;
            }
        }
        assert (p != -1);
        assert (abs(A[p][k]) > eps);
        if (k != p) {
            for (int j = 0; j < N; j++)
                swap(A[k][j], A[p][j]);
            swap(b[k], b[p]);
        }
        for (int i = 0; i < N; i++) if (i != k) {
            long double r = A[i][k] / A[k][k];
            for (int j = 0; j < N; j++)
                A[i][j] -= A[k][j] * r;
            b[i] -= b[k] * r;
        }
    }
    for (int i = 0; i < N; i++) {
        b[i] /= A[i][i];
        A[i][i] = 1;
    }
    cout << fixed << setprecision(20);
    cout << b[0] << '\n';
}