#define MOD_TYPE 2

#include <bits/stdc++.h>
using namespace std;

//#include <atcoder/all>
#include <atcoder/modint>
//#include <atcoder/lazysegtree>
//#include <atcoder/segtree>

using namespace atcoder;

#if 0
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
using Int = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
#endif

#if 0
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tag_and_trait.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
using namespace __gnu_pbds;
using namespace __gnu_cxx;
template <typename T>
using extset =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#endif

#if 0
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif

#pragma region Macros

using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;

#if MOD_TYPE == 1
constexpr ll MOD = ll(1e9 + 7);
#else
#if MOD_TYPE == 2
constexpr ll MOD = 998244353;
#else
constexpr ll MOD = 1000003;
#endif
#endif

using mint = static_modint<MOD>;
constexpr int INF = (int)1e9 + 10;
constexpr ll LINF = (ll)4e18;
constexpr double PI = acos(-1.0);
constexpr double EPS = 1e-11;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};

#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define possible(n) cout << ((n) ? "possible" : "impossible") << "\n"
#define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";
#define UNIQUE(v) v.erase(unique(all(v)), v.end())

struct io_init {
  io_init() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(30) << setiosflags(ios::fixed);
  };
} io_init;
template <typename T>
inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
inline ll floor(ll a, ll b) {
  if (b < 0) a *= -1, b *= -1;
  if (a >= 0) return a / b;
  return -((-a + b - 1) / b);
}
inline ll ceil(ll a, ll b) { return floor(a + b - 1, b); }
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val) {
  fill((T *)array, (T *)(array + N), val);
}
template <typename T>
vector<T> compress(vector<T> &v) {
  vector<T> val = v;
  sort(all(val)), val.erase(unique(all(val)), val.end());
  for (auto &&vi : v) vi = lower_bound(all(val), vi) - val.begin();
  return val;
}
template <typename T, typename U>
constexpr istream &operator>>(istream &is, pair<T, U> &p) noexcept {
  is >> p.first >> p.second;
  return is;
}
template <typename T, typename U>
constexpr ostream &operator<<(ostream &os, pair<T, U> p) noexcept {
  os << p.first << " " << p.second;
  return os;
}
ostream &operator<<(ostream &os, mint m) {
  os << m.val();
  return os;
}
ostream &operator<<(ostream &os, modint m) {
  os << m.val();
  return os;
}
template <typename T>
constexpr istream &operator>>(istream &is, vector<T> &v) noexcept {
  for (int i = 0; i < v.size(); i++) is >> v[i];
  return is;
}
template <typename T>
constexpr ostream &operator<<(ostream &os, vector<T> &v) noexcept {
  for (int i = 0; i < v.size(); i++)
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  return os;
}
template <typename T>
constexpr void operator--(vector<T> &v, int) noexcept {
  for (int i = 0; i < v.size(); i++) v[i]--;
}

random_device seed_gen;
mt19937_64 engine(seed_gen());

struct BiCoef {
  vector<mint> fact_, inv_, finv_;
  BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
    fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
    for (int i = 2; i < n; i++) {
      fact_[i] = fact_[i - 1] * i;
      inv_[i] = -inv_[MOD % i] * (MOD / i);
      finv_[i] = finv_[i - 1] * inv_[i];
    }
  }
  mint C(ll n, ll k) const noexcept {
    if (n < k || n < 0 || k < 0) return 0;
    return fact_[n] * finv_[k] * finv_[n - k];
  }
  mint P(ll n, ll k) const noexcept { return C(n, k) * fact_[k]; }
  mint H(ll n, ll k) const noexcept { return C(n + k - 1, k); }
  mint Ch1(ll n, ll k) const noexcept {
    if (n < 0 || k < 0) return 0;
    mint res = 0;
    for (int i = 0; i < n; i++)
      res += C(n, i) * mint(n - i).pow(k) * (i & 1 ? -1 : 1);
    return res;
  }
  mint fact(ll n) const noexcept {
    if (n < 0) return 0;
    return fact_[n];
  }
  mint inv(ll n) const noexcept {
    if (n < 0) return 0;
    return inv_[n];
  }
  mint finv(ll n) const noexcept {
    if (n < 0) return 0;
    return finv_[n];
  }
};

BiCoef bc(200010);

#pragma endregion

// -------------------------------

#pragma region ImplicitTreap

// T0: 元の配列のモノイド
// T1: T0に対する作用素モノイド
template <class T0, class T1>
class BaseImplicitTreap {
  // T0上の演算、単位元
  virtual T0 f0(T0, T0) = 0;
  const T0 u0;
  // T1上の演算、単位元
  virtual T1 f1(T1, T1) = 0;
  const T1 u1;
  // T0に対するT1の作用
  virtual T0 g(T0, T1) = 0;
  // 多数のt1(T1)に対するf1の合成
  virtual T1 p(T1, int) = 0;

  class xorshift {
    uint64_t x;

   public:
    xorshift() {
      mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
      x = rnd();
      for (int i = 0; i < 100; i++) {
        random();
      }
    }

    uint64_t random() {
      x = x ^ (x << 7);
      return x = x ^ (x >> 9);
    }
  } rnd;

  struct Node {
    T0 value, acc;
    T1 lazy;
    int priority, cnt;
    bool rev;
    Node *l, *r;

    Node(T0 value_, int priority_, T0 u0_, T1 u1_)
        : value(value_),
          acc(u0_),
          lazy(u1_),
          priority(priority_),
          cnt(1),
          rev(false),
          l(nullptr),
          r(nullptr) {}
  } *root = nullptr;

  using Tree = Node *;

  int cnt(Tree t) { return t ? t->cnt : 0; }

  T0 acc(Tree t) { return t ? t->acc : u0; }

  void update_cnt(Tree t) {
    if (t) {
      t->cnt = 1 + cnt(t->l) + cnt(t->r);
    }
  }

  void update_acc(Tree t) {
    if (t) {
      t->acc = f0(acc(t->l), f0(t->value, acc(t->r)));
    }
  }

  void pushup(Tree t) { update_cnt(t), update_acc(t); }

  void pushdown(Tree t) {
    if (t && t->rev) {
      t->rev = false;
      swap(t->l, t->r);
      if (t->l) t->l->rev ^= 1;
      if (t->r) t->r->rev ^= 1;
    }
    if (t && t->lazy != u1) {
      if (t->l) {
        t->l->lazy = f1(t->l->lazy, t->lazy);
        t->l->acc = g(t->l->acc, p(t->lazy, cnt(t->l)));
      }
      if (t->r) {
        t->r->lazy = f1(t->r->lazy, t->lazy);
        t->r->acc = g(t->r->acc, p(t->lazy, cnt(t->r)));
      }
      t->value = g(t->value, p(t->lazy, 1));
      t->lazy = u1;
    }
    pushup(t);
  }

  void split(Tree t, int key, Tree &l, Tree &r) {
    if (!t) {
      l = r = nullptr;
      return;
    }
    pushdown(t);
    int implicit_key = cnt(t->l) + 1;
    if (key < implicit_key) {
      split(t->l, key, l, t->l), r = t;
    } else {
      split(t->r, key - implicit_key, t->r, r), l = t;
    }
    pushup(t);
  }

  void insert(Tree &t, int key, Tree item) {
    Tree t1, t2;
    split(t, key, t1, t2);
    merge(t1, t1, item);
    merge(t, t1, t2);
  }

  void merge(Tree &t, Tree l, Tree r) {
    pushdown(l);
    pushdown(r);
    if (!l || !r) {
      t = l ? l : r;
    } else if (l->priority > r->priority) {
      merge(l->r, l->r, r), t = l;
    } else {
      merge(r->l, l, r->l), t = r;
    }
    pushup(t);
  }

  void erase(Tree &t, int key) {
    Tree t1, t2, t3;
    split(t, key + 1, t1, t2);
    split(t1, key, t1, t3);
    merge(t, t1, t2);
  }

  void update(Tree t, int l, int r, T1 x) {
    if (l >= r) return;
    Tree t1, t2, t3;
    split(t, l, t1, t2);
    split(t2, r - l, t2, t3);
    t2->lazy = f1(t2->lazy, x);
    t2->acc = g(t2->acc, p(x, cnt(t2)));
    merge(t2, t2, t3);
    merge(t, t1, t2);
  }

  T0 query(Tree t, int l, int r) {
    if (l == r) return u0;
    Tree t1, t2, t3;
    split(t, l, t1, t2);
    split(t2, r - l, t2, t3);
    T0 ret = t2->acc;
    merge(t2, t2, t3);
    merge(t, t1, t2);
    return ret;
  }

  // [l, r)の中で左から何番目か
  int find(Tree t, T0 x, int offset, bool left = true) {
    if (f0(t->acc, x) == x) {
      return -1;
    } else {
      if (left) {
        if (t->l && f0(t->l->acc, x) != x) {
          return find(t->l, x, offset, left);
        } else {
          return (f0(t->value, x) != x)
                     ? offset + cnt(t->l)
                     : find(t->r, x, offset + cnt(t->l) + 1, left);
        }
      } else {
        if (t->r && f0(t->r->acc, x) != x) {
          return find(t->r, x, offset + cnt(t->l) + 1, left);
        } else {
          return (f0(t->value, x) != x) ? offset + cnt(t->l)
                                        : find(t->l, x, offset, left);
        }
      }
    }
  }

  void reverse(Tree t, int l, int r) {
    if (l > r) return;
    Tree t1, t2, t3;
    split(t, l, t1, t2);
    split(t2, r - l, t2, t3);
    t2->rev ^= 1;
    merge(t2, t2, t3);
    merge(t, t1, t2);
  }

  // [l, r)の先頭がmになるようにシフトさせる。std::rotateと同じ仕様
  void rotate(Tree t, int l, int m, int r) {
    reverse(t, l, r);
    reverse(t, l, l + r - m);
    reverse(t, l + r - m, r);
  }

  void dump(Tree t) {
    if (!t) return;
    pushdown(t);
    dump(t->l);
    cout << t->value << " ";
    dump(t->r);
  }

 public:
  BaseImplicitTreap(T0 u0_, T1 u1_) : u0(u0_), u1(u1_) {}

  void set_by_vector(const vector<T0> &a) {
    for (int i = 0; i < a.size(); i++) {
      insert(i, a[i]);
    }
  }

  int size() { return cnt(root); }

  void insert(int pos, T0 x) {
    insert(root, pos, new Node(x, rnd.random(), u0, u1));
  }

  void update(int l, int r, T1 x) { update(root, l, r, x); }

  T0 query(int l, int r) { return query(root, l, r); }

  // 二分探索。[l, r)内のkでf0(tr[k], x) !=
  // xとなる最左/最右のもの。存在しない場合は-1
  // たとえばMinMonoidの場合、x未満の最左/最右の要素の位置を返す
  int binary_search(int l, int r, T0 x, bool left = true) {
    if (l >= r) return -1;
    Tree t1, t2, t3;
    split(root, l, t1, t2);
    split(t2, r - l, t2, t3);
    int ret = find(t2, x, l, left);
    merge(t2, t2, t3);
    merge(root, t1, t2);
    return ret;
  }

  void erase(int pos) { erase(root, pos); }

  void reverse(int l, int r) { reverse(root, l, r); }

  void rotate(int l, int m, int r) { rotate(root, l, m, r); }

  void dump() {
    dump(root);
    cout << "\n";
  }

  T0 operator[](int pos) { return query(pos, pos + 1); }
};

template <class T0, class T1>
struct MinUpdateQuery : public BaseImplicitTreap<T0, T1> {
  using BaseImplicitTreap<T0, T1>::BaseImplicitTreap;
  MinUpdateQuery()
      : MinUpdateQuery(numeric_limits<T0>::max(), numeric_limits<T1>::min()) {}
  T0 f0(T0 x, T0 y) override { return min(x, y); }
  T1 f1(T1 x, T1 y) override { return y == numeric_limits<T1>::min() ? x : y; }
  T0 g(T0 x, T1 y) override { return y == numeric_limits<T1>::min() ? x : y; }
  T1 p(T1 x, int len) override { return x; }
};

template <class T0, class T1>
struct SumAddQuery : public BaseImplicitTreap<T0, T1> {
  using BaseImplicitTreap<T0, T1>::BaseImplicitTreap;
  SumAddQuery() : SumAddQuery(0, 0) {}
  T0 f0(T0 x, T0 y) override { return x + y; }
  T1 f1(T1 x, T1 y) override { return x + y; }
  T0 g(T0 x, T1 y) override { return x + y; }
  T1 p(T1 x, int len) override { return x * len; }
};

template <class T0, class T1>
struct MinAddQuery : public BaseImplicitTreap<T0, T1> {
  using BaseImplicitTreap<T0, T1>::BaseImplicitTreap;
  MinAddQuery() : MinAddQuery(numeric_limits<T0>::max(), 0) {}
  T0 f0(T0 x, T0 y) override { return min(x, y); }
  T1 f1(T1 x, T1 y) override { return x + y; }
  T0 g(T0 x, T1 y) override { return x + y; }
  T1 p(T1 x, int len) override { return x; }
};

template <class T0, class T1>
struct SumUpdateQuery : public BaseImplicitTreap<T0, T1> {
  using BaseImplicitTreap<T0, T1>::BaseImplicitTreap;
  SumUpdateQuery() : SumUpdateQuery(0, numeric_limits<T1>::min()) {}
  T0 f0(T0 x, T0 y) override { return x + y; }
  T1 f1(T1 x, T1 y) override { return y == numeric_limits<T1>::min() ? x : y; }
  T0 g(T0 x, T1 y) override { return y == numeric_limits<T1>::min() ? x : y; }
  T1 p(T1 x, int len) override {
    return x == numeric_limits<T1>::min() ? numeric_limits<T1>::min() : x * len;
  }
};

template <class T0>
struct SumAffineQuery : public BaseImplicitTreap<T0, pair<T0, T0>> {
  using T1 = pair<T0, T0>;  // first * x + second
  using BaseImplicitTreap<T0, T1>::BaseImplicitTreap;
  SumAffineQuery() : SumAffineQuery(0, {1, 0}) {}
  T0 f0(T0 x, T0 y) override { return x + y; }
  T1 f1(T1 x, T1 y) override {
    return {x.first * y.first, x.second * y.first + y.second};
  }
  T0 g(T0 x, T1 y) override { return y.first * x + y.second; }
  T1 p(T1 x, int len) override { return {x.first, x.second * len}; }
  // update(i, j, {a, b}); // [i, j)にax + bを作用
  // update(i, j, {0, a}); // update
  // update(i, j, {1, a}); // 加算
  // update(i, j, {a, 0}); // 倍
};

template <class T>
struct MinmaxAffineQuery : public BaseImplicitTreap<pair<T, T>, pair<T, T>> {
  using T0 = pair<T, T>;  // {min, max}
  using T1 = pair<T, T>;  // first * x + second
  using BaseImplicitTreap<T0, T1>::BaseImplicitTreap;
  MinmaxAffineQuery()
      : MinmaxAffineQuery({numeric_limits<T>::max(), -numeric_limits<T>::max()},
                          {1, 0}) {
  }  // TODO: _u1を使うとコンパイル通らない原因不明
  T0 f0(T0 x, T0 y) override {
    return {min(x.first, y.first), max(x.second, y.second)};
  }
  T1 f1(T1 x, T1 y) override {
    return {x.first * y.first, x.second * y.first + y.second};
  }
  T0 g(T0 x, T1 y) override {
    T0 ret = {x.first * y.first + y.second, x.second * y.first + y.second};
    if (y.first < 0) swap(ret.first, ret.second);
    return ret;
  }
  T1 p(T1 x, int len) override { return x; }
  // update(i, j, {a, b}); // [i, j)にax + bを作用
  // update(i, j, {0, a}); // update
  // update(i, j, {1, a}); // 加算
  // update(i, j, {a, 0}); // 倍
};

// https://xuzijian629.hatenablog.com/entry/2019/10/25/234938

#pragma endregion

void solve() {
  int n;
  string s;
  cin >> n >> s;
  const string AGCT = "AGCT";
  vector<int> AGCT_int;
  for (auto c : AGCT) AGCT_int.push_back(c - 'A');
  int cnt[26] = {};
  for (auto c : s) cnt[c - 'A']++;

  modint::set_mod(26);
  vector<modint> si(n);
  rep(i, n) si[i] = s[i] - 'A';
  SumAddQuery<modint, int> treap;
  treap.set_by_vector(si);

  int ans = 0;
  int len = n;
  while (1) {
    int sum = 0;
    for (auto i : AGCT_int) {
      sum += cnt[i];
    }
    if (sum == 0) break;
    ans++;
    int del = treap[sum - 1].val();
    cnt[del]--;
    treap.erase(sum - 1);
    len--;
    treap.update(0, len, cnt[del]);
    rotate(cnt, cnt + 26 - cnt[del] % 26, cnt + 26);
  }
  cout << ans << "\n";
}

int main() { solve(); }