#include<bits/stdc++.h>
#define ld long double
#define int long long
using namespace std;
int n, m, k;
long long cnt;
inline ld ksm(ld p, int q) {
	ld ans = 1;
	while (q) {
		if (q & 1) ans = ans * p;
		q >>= 1;
		p = p * p;
	}
	return ans;
}
signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin >> k >> n >> m;
	cnt = n * m * ( n * m - 1) + n * m;
	ld ans = 0;
	int op = 0, u, v, p, q;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			op = 0;
			u = i - 1, v = j - 1, p = n - i, q = m - j;
			op = u * u * m * m + v * v * n * n + p * p * m * m + q * q * n * n;
			op -= u * u * v * v + u * u * q * q + p * p * v * v + p * p * q * q;
			ans += 1 - ksm( 1.0 * op / cnt, k);;
		}
	}
	cout << fixed << setprecision(2) << ans;

}