#include using namespace std; using ll = long long; static const int MOD = 998244353; ll modpow(ll a, ll e) { ll r = 1; while (e > 0) { if (e & 1) r = r * a % MOD; a = a * a % MOD; e >>= 1; } return r; } struct Comb { vector fact, ifact; void init(int n) { fact.assign(n + 1, 1); ifact.assign(n + 1, 1); for (int i = 1; i <= n; i++) fact[i] = (ll)fact[i - 1] * i % MOD; ifact[n] = (int)modpow(fact[n], MOD - 2); for (int i = n; i >= 1; i--) ifact[i - 1] = (ll)ifact[i] * i % MOD; } int C(int n, int r) const { if (r < 0 || r > n) return 0; return (ll)fact[n] * ifact[r] % MOD * ifact[n - r] % MOD; } }; static inline void trim(vector &a) { while (!a.empty() && a.back() == 0) a.pop_back(); } vector mul_qs_minus_1(const vector &p, int s, int E) { if (p.empty()) return {}; int need = min(E + 1, (int)p.size() + s); vector res(need, 0); // p(q) * q^s if (s <= E) { int lim = min((int)p.size(), E + 1 - s); for (int i = 0; i < lim; i++) res[i + s] = p[i]; } // - p(q) int lim = min((int)p.size(), need); for (int i = 0; i < lim; i++) { res[i] -= p[i]; if (res[i] < 0) res[i] += MOD; } //trim(res); return res; } void add_shift_scaled(vector &dst, const vector &src, int shift, int scale, int E) { //if (src.empty() || scale == 0 || shift > E) return; int need = min(E + 1, shift + (int)src.size()); if ((int)dst.size() < need) dst.resize(need, 0); int len = need - shift; for (int i = 0; i < len; i++) { //if (src[i] == 0) continue; dst[i + shift] = (dst[i + shift] + (ll)src[i] * scale) % MOD; } } int main() { int N, M, K; cin >> N >> M >> K; int E = N * (N - 1) / 2; int R = E - M; int S = N - 2; Comb comb; comb.init(E); // dp[r][s] is a polynomial in q. // r: number of ordinary vertices not reached yet // s: size of current BFS frontier vector>> dp(S + 1, vector>(S + 2)); dp[S][1] = vector{1}; // Build layers 1,2,...,K-1 without reaching vertex N. for (int step = 0; step < K - 1; step++) { vector>> ndp(S + 1, vector>(S + 2)); for (int r = 0; r <= S; r++) { for (int s = 0; s <= S + 1; s++) { //if (dp[r][s].empty()) continue; vector cur = dp[r][s]; // cur * (q^s - 1)^t for (int t = 0; t <= r; t++) { int shift = t * (t - 1) / 2; // free edges inside the next frontier int ways = comb.C(r, t); add_shift_scaled(ndp[r - t][t], cur, shift, ways, E); if (t != r) cur = mul_qs_minus_1(cur, s, E); } } } dp.swap(ndp); } // H(q): generating polynomial for dist(1,N)=K in q=1+x. vector H(E + 1, 0); // N must have at least one edge to the current frontier: (q^s - 1). // All edges among the remaining r vertices, between them and N, and between them and the current frontier are free. for (int r = 0; r <= S; r++) { for (int s = 0; s <= S + 1; s++) { const vector &p = dp[r][s]; //if (p.empty()) continue; int base = s * r + r + r * (r - 1) / 2; for (int i = 0; i < (int)p.size(); i++) { int val = p[i]; if (val == 0) continue; if (i + base + s <= E) { H[i + base + s] += val; if (H[i + base + s] >= MOD) H[i + base + s] -= MOD; } if (i + base <= E) { H[i + base] -= val; if (H[i + base] < 0) H[i + base] += MOD; } } } } // We need [x^R] H(1+x). If H(q)=sum_c h_c q^c, then // [x^R] H(1+x) = sum_c h_c * C(c,R). ll ans = 0; for (int c = R; c <= E; c++) { if (H[c] == 0) continue; ans += (ll)H[c] * comb.C(c, R) % MOD; ans %= MOD; } cout << ans % MOD << '\n'; return 0; }