Beispiel #1
0
        public void Run()
        {
            {
                var line = Input.ReadLongArray();
                N = line[0];
                A = line[1];
                B = line[2];
                K = line[3];
            }

            var  comb = new FermatCombination(300000);
            long ret  = 0;

            for (long a = 0; a <= N; a++)
            {
                long R = K - a * A;
                if (R >= 0 && R % B == 0 && R / B <= N)
                {
                    long b = R / B;
                    ret += comb.Combination(N, a) * comb.Combination(N, b);
                    ret %= M;
                }
            }

            Console.WriteLine(ret);
        }
Beispiel #2
0
        public void Run()
        {
            var comb = new FermatCombination(1000000);

            N = Input.ReadInt();

            long ret = 0;

            {
                var v = comb.Permutation(N - 1, N - 1);
                ret += (v * (N)) % MOD;
                ret %= MOD;
            }

            for (int k = 0; k < N; k++)
            {
                // C(K ? 1, N ? 1 ? K) × K! × (N ? 1 ? K)!

                if (k - 1 < N - 1 - k)
                {
                    continue;
                }
                var v1 = comb.Combination(k - 1, N - 1 - k);
                var v2 = comb.Permutation(k, k);
                var v3 = comb.Permutation(N - 1 - k, N - 1 - k);
                var v  = (((v1 * v2) % MOD) * v3) % MOD;
                ret += (MOD - v);
                ret %= MOD;
            }

            Console.WriteLine(ret);
        }