#include <iostream> #include <vector> #include <algorithm> #include <cmath> #include <string> #include <queue> #include <stack> #include <set> #include <map> #include <iomanip> #include <utility> #include <tuple> #include <functional> #include <bitset> #include <cassert> #include <complex> #include <stdio.h> #include <time.h> #include <numeric> #include <random> #include <unordered_map> #include <unordered_set> #define all(a) a.begin(),a.end() #define rep(i, n) for (ll i = 0; i < (n); i++) #define pb push_back #define debug(x) cerr << __LINE__ << ' ' << #x << ':' << x << '\n' #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") using namespace std; typedef long long ll; typedef unsigned long long ull; typedef long double ld; typedef pair<ll, ll> P; typedef complex<ld> com; constexpr int inf = 1000000010; constexpr ll INF = 1000000000000000010; constexpr ld eps = 1e-12; constexpr ld pi = 3.141592653589793238; template<class T, class U> inline bool chmax(T &a, const U &b) { if (a < b) { a = b; return true; } return false; } template<class T, class U> inline bool chmin(T &a, const U &b) { if (a > b) { a = b; return true; } return false; } constexpr ll mod = 998244353; constexpr ll root = 3; vector<ll> fac, inv, facinv; void modcalc(int n) { fac.resize(n); inv.resize(n); facinv.resize(n); fac[0] = 1; fac[1] = 1; inv[1] = 1; facinv[0] = 1; facinv[1] = 1; for (ll i = 2; i < n; i++) { fac[i] = fac[i - 1] * i % mod; inv[i] = mod - inv[mod % i] * (mod / i) % mod; facinv[i] = facinv[i - 1] * inv[i] % mod; } } ll modinv(ll a) { a %= mod; if (a == 0) abort(); if (a < (ll)inv.size()) return inv[a]; ll b = mod, u = 1, v = 0; while (b) { ll t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); } u %= mod; if (u < 0) u += mod; return u; } ll modpow(ll a, ll b, ll m = mod) { ll ans = 1; a %= m; while (b) { if (b & 1) ans = ans * a % m; a = a * a % m; b >>= 1; } return ans; } ll modcomb(ll n, ll k) { if (n < 0 || k < 0 || n < k) return 0; return fac[n] * facinv[k] % mod * facinv[n - k] % mod; } ll modperm(ll n, ll k) { if (n < 0 || k < 0 || n < k) return 0; return fac[n] * facinv[n - k] % mod; } ll modhom(ll n, ll k) { if (n < 0 || k < 0 || n == 0 && k > 0) return 0; if (n == 0 && k == 0) return 1; return fac[n + k - 1] * facinv[k] % mod * facinv[n - 1] % mod; } void ntt(vector<ll> &f, bool inv) { int n = f.size(); int h = modpow(root, (mod - 1) / n, mod); if (inv) h = modinv(h); for (int i = 0, j = 1; j < n - 1; ++j) { for (int k = n >> 1; k > (i ^= k); k >>= 1); if (j < i) swap(f[i], f[j]); } for (int i = 1, j = 2; i < n; i *= 2, j *= 2) { ll w = 1, base = modpow(h, n / j, mod); for (int k = 0; k < i; ++k, (w *= base) %= mod) { for (int l = k; l < n; l += j) { ll u = f[l]; ll d = f[l + i] * w % mod; f[l] = u + d; if (f[l] >= mod) f[l] -= mod; f[l + i] = u - d; if (f[l + i] < 0) f[l + i] += mod; } } } for (ll &x : f) if (x < 0) x += mod; } vector<ll> convolution(vector<ll> f, vector<ll> g) { int n = 1; while (n < f.size() + g.size() + 2) n <<= 1; f.resize(n); g.resize(n); ntt(f, false); ntt(g, false); vector<ll> res(n); for (int i = 0; i < n; i++) res[i] = f[i] * g[i] % mod; ntt(res, true); ll inv = modinv(n); for (int i = 0; i < n; i++) res[i] = res[i] * inv % mod; return res; } int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); modcalc(500010); string s; cin >> s; vector<int> cnt(26); for (char c : s) cnt[c - 'a']++; sort(all(cnt)); vector<ll> f(1, 1); rep(i, 26) { int sz = cnt[i] + 1; vector<ll> v(sz); rep(j, sz) v[j] = facinv[j]; f = convolution(f, v); int re = 1; rep(j, i + 1) re += cnt[j]; f.resize(re); } ll ans = 0; for (int i = 1; i <= s.size(); i++) { ans += f[i] * fac[i]; ans %= mod; } cout << ans << '\n'; }