#include using namespace std; #define rep(i, n) for(int i = 0; i < n; i++) #define rep2(i, x, n) for(int i = x; i <= n; i++) #define rep3(i, x, n) for(int i = x; i >= n; i--) #define each(e, v) for(auto &e: v) #define pb push_back #define eb emplace_back #define all(x) x.begin(), x.end() #define rall(x) x.rbegin(), x.rend() #define sz(x) (int)x.size() using ll = long long; using pii = pair; using pil = pair; using pli = pair; using pll = pair; //const int MOD = 1000000007; const int MOD = 998244353; const int inf = (1<<30)-1; const ll INF = (1LL<<60)-1; template bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;}; template bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;}; struct io_setup{ io_setup(){ ios_base::sync_with_stdio(false); cin.tie(NULL); cout << fixed << setprecision(15); } } io_setup; template struct Mod_Int{ int x; Mod_Int() : x(0) {} Mod_Int(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {} Mod_Int &operator += (const Mod_Int &p){ if((x += p.x) >= mod) x -= mod; return *this; } Mod_Int &operator -= (const Mod_Int &p){ if((x += mod - p.x) >= mod) x -= mod; return *this; } Mod_Int &operator *= (const Mod_Int &p){ x = (int) (1LL * x * p.x % mod); return *this; } Mod_Int &operator /= (const Mod_Int &p){ *this *= p.inverse(); return *this; } Mod_Int &operator ++ () {return *this += Mod_Int(1);} Mod_Int operator ++ (int){ Mod_Int tmp = *this; ++*this; return tmp; } Mod_Int &operator -- () {return *this -= Mod_Int(1);} Mod_Int operator -- (int){ Mod_Int tmp = *this; --*this; return tmp; } Mod_Int operator - () const {return Mod_Int(-x);} Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;} Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;} Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;} Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;} bool operator == (const Mod_Int &p) const {return x == p.x;} bool operator != (const Mod_Int &p) const {return x != p.x;} Mod_Int inverse() const{ assert(*this != Mod_Int(0)); return pow(mod-2); } Mod_Int pow(long long k) const{ Mod_Int now = *this, ret = 1; for(; k > 0; k >>= 1, now *= now){ if(k&1) ret *= now; } return ret; } friend ostream &operator << (ostream &os, const Mod_Int &p){ return os << p.x; } friend istream &operator >> (istream &is, Mod_Int &p){ long long a; is >> a; p = Mod_Int(a); return is; } }; using mint = Mod_Int; template struct Combination{ using T = Mod_Int; vector _fac, _ifac; Combination(int n){ _fac.resize(n+1), _ifac.resize(n+1); _fac[0] = 1; for(int i = 1; i <= n; i++) _fac[i] = _fac[i-1]*i; _ifac[n] = _fac[n].inverse(); for(int i = n; i >= 1; i--) _ifac[i-1] = _ifac[i]*i; } T fac(int k) const {return _fac[k];} T ifac(int k) const {return _ifac[k];} T comb(int n, int k) const{ if(k < 0 || n < k) return 0; return fac(n)*ifac(n-k)*ifac(k); } T comb2(int x, int y) const {return comb(x+y, x);} T perm(int n, int k) const{ if(k < 0 || n < k) return 0; return fac(n)*ifac(n-k); } T second_stirling_number(int n, int k) const{ //n個の区別できる玉を、k個の区別しない箱に、各箱に1個以上玉が入るように入れる場合の数 T ret = 0; for(int i = 0; i <= k; i++){ T tmp = comb(k, i)*T(i).pow(n); ret += ((k-i)&1)? -tmp : tmp; } return ret*ifac(k); } T bell_number(int n, int k) const{ //n個の区別できる玉を、k個の区別しない箱に入れる場合の数 if(n == 0) return 1; k = min(k, n); vector pref(k+1); pref[0] = 1; for(int i = 1; i <= k; i++){ if(i&1) pref[i] = pref[i-1]-ifac(i); else pref[i] = pref[i-1]+ifac(i); } T ret = 0; for(int i = 1; i <= k; i++){ ret += T(i).pow(n)*ifac(i)*pref[k-i]; } return ret; } }; using comb = Combination; set s; void dfs(string S){ int n = sz(S); rep(k, n) rep(j, k) rep(i, j){ string T; if(S[i] == 'a' && S[j] == 'b' && S[k] == 'c'){ T = S; T[i] = 'b', T[j] = 'c', T[k] = 'a'; } if(S[i] == 'b' && S[j] == 'c' && S[k] == 'a'){ T = S; T[i] = 'c', T[j] = 'a', T[k] = 'b'; } if(S[i] == 'c' && S[j] == 'a' && S[k] == 'b'){ T = S; T[i] = 'a', T[j] = 'b', T[k] = 'c'; } if(!empty(T)){ if(!s.count(T)) s.emplace(T), dfs(T); } } } int main(){ int N; string S; cin >> N >> S; vector> ids(3); rep(i, N){ ids[S[i]-'A'].eb(i); } bool flag = false; rep(i, 3){ int p = 0; bool tmp = true; rep(j, 3){ int k = (i+j)%3; if(empty(ids[k]) || ids[k].back() < p) {tmp = false; break;} p = *lower_bound(all(ids[k]), p); } if(tmp) flag = true; } if(!flag) {cout << "1\n"; return 0;} comb C(N); mint ans = C.fac(N); rep(i, 3) ans *= C.ifac(sz(ids[i])); ans -= N; cout << ans << '\n'; }