提出 #4876314

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ソースコード 拡げる

#include <bits/stdc++.h>
using namespace std;

using VS = vector<string>;    using LL = long long;
using VI = vector<int>;       using VVI = vector<VI>;
using PII = pair<int, int>;   using PLL = pair<LL, LL>;
using VL = vector<LL>;        using VVL = vector<VL>;

#define ALL(a)  begin((a)),end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))
#define FOR(i, s, e) for (int(i) = (s); (i) < (e); (i)++)
#define FORR(i, s, e) for (int(i) = (s); (i) > (e); (i)--)
//#pragma GCC optimize ("-O3") 
#ifdef YANG33
#include "mydebug.hpp"
#else
#define DD(x) 
#endif
const int INF = 1e9;                          const LL LINF = 1e16;
const LL MOD = 1000000007;                    const double PI = acos(-1.0);

/* -----  2019/04/07  Problem: ABC 028 D / Link: http://abc028.contest.atcoder.jp/tasks/abc028_d  ----- */


int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);

	double N, K; cin >> N >> K;
	double ans = ((6 * (K - 1)*(N - K)) + (3 * (N - 1)) + (1)) / (N*N*N);

	cout << fixed << setprecision(10) << ans << endl;

	return 0;
}

提出情報

ジャッジ結果