#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for (auto i=(a); i<(b); ++i)
#define iter(it,c) for (auto it = (c).begin(); it != (c).end(); ++it)
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef long long ll;
const int INF = 2147483647;

int main() {
    int n, i, k;
    cin >> n >> i >> k;

    long double sm = 0;
    for (int j = 1; j < i; j++) {
        sm += (pow(j * 1.0 / n, k) - pow((j - 1) * 1.0 / n, k)) * i;
    }
    for (int j = i; j <= n; j++) {
        sm += (pow(j * 1.0 / n, k) - pow((j - 1) * 1.0 / n, k)) * ((j + 1) / 2.0);
    }

    cout << setprecision(12) << sm << endl;

    return 0;
}