#include #include #include #include using namespace std; using Mint = atcoder::modint998244353; using Mat = vector>; Mat mul(Mat a, Mat b) { int N = a.size(); Mat c(N, vector(N, 0)); for (int i = 0; i < N; i++) for (int j = 0; j < N; j++) for (int k = 0; k < N; k++) c[i][k] += a[i][j] * b[j][k]; return c; } Mat I(int N) { Mat a(N, vector(N, 0)); for (int i = 0; i < N; i++) a[i][i] = 1; return a; } Mat pow(Mat a, int b) { if (b == 0) return I(a.size()); if (b == 1) return a; Mat r = pow(a, b / 2); r = mul(r, r); if (b & 1) r = mul(r, a); return r; } int main() { string S; int K; cin >> S >> K; int HN = S.size() / 2; Mat M(HN + 1, vector(HN + 1, 0)); for (int i = 0; i <= HN; i++) { // curr diff: 2*i M[i][i] = HN * (HN - 1) + 2 * i * (HN - i); if (i != HN) M[i + 1][i] = (HN - i) * (HN - i); if (i != 0) M[i - 1][i] = i * i; } M = pow(M, K); Mat DP(1, vector(1, 1)); for (int i = 0; i < (int)S.size(); i++) { Mat N(i + 2, vector(i + 2)); // prefix sum = j, total difference = k for (int j = 0; j <= i; j++) for (int k = 0; k <= i; k++) { // choose '(' { int new_j = j + 1; int new_k = k + (S[i] != '('); if (new_j >= 0 && new_k >= 0) N[new_j][new_k] += DP[j][k]; } // choose ')' { int new_j = j - 1; int new_k = k + (S[i] != ')'); if (new_j >= 0 && new_k >= 0) N[new_j][new_k] += DP[j][k]; } } DP = N; } Mat C(HN + 1, vector(HN + 1)); for (int i = 0; i <= HN; i++) { C[i][i] = C[i][0] = 1; for (int j = 1; j < i; j++) C[i][j] = C[i - 1][j - 1] + C[i - 1][j]; } Mint ans = 0; for (int i = 0; i <= HN; i++) ans += M[i][0] * DP[0][2 * i] * (C[HN][i] * C[HN][i]).inv(); cout << ans.val() << endl; }