// yukicoder/1951/main.cpp
// author: @___Johniel
// github: https://github.com/johniel/

#include <bits/stdc++.h>

#define each(i, c) for (auto& i : c)
#define unless(cond) if (!(cond))
// #define endl "\n"

using namespace std;

template<typename P, typename Q> ostream& operator << (ostream& os, pair<P, Q> p) { os << "(" << p.first << "," << p.second << ")"; return os; }
template<typename P, typename Q> istream& operator >> (istream& is, pair<P, Q>& p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator << (ostream& os, vector<T> v) { os << "("; for (auto& i: v) os << i << ","; os << ")"; return os; }
template<typename T> istream& operator >> (istream& is, vector<T>& v) { for (auto& i: v) is >> i; return is; }
template<typename T> ostream& operator << (ostream& os, set<T> s) { os << "#{"; for (auto& i: s) os << i << ","; os << "}"; return os; }
template<typename K, typename V> ostream& operator << (ostream& os, map<K, V> m) { os << "{"; for (auto& i: m) os << i << ","; os << "}"; return os; }

template<typename T> inline T setmax(T& a, T b) { return a = std::max(a, b); }
template<typename T> inline T setmin(T& a, T b) { return a = std::min(a, b); }

using lli = long long int;
using ull = unsigned long long;
using point = complex<double>;
using str = string;
template<typename T> using vec = vector<T>;

constexpr array<int, 8> di({0, 1, -1, 0, 1, -1, 1, -1});
constexpr array<int, 8> dj({1, 0, 0, -1, 1, -1, -1, 1});
constexpr lli mod = 1e9 + 7;
// constexpr lli mod = 998244353;

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;

template<typename T>
class ordered_set : public tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update> {};


int main(int argc, char *argv[])
{
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.setf(ios_base::fixed);
  cout.precision(15);

  int n;
  str s;
  while (cin >> n >> s) {
    ordered_set<pair<int, char>> t;
    for (int i = 0; i < s.size(); ++i) {
      t.insert(make_pair(i, s[i]));
    }
    map<char, int> m;
    each (i, s) ++m[i];

    int c = 0;
    int z = 0;
    while (true) {
      int d = m['A'] + m['G'] + m['C'] + m['T'];
      if (d == 0) break;
      ++z;
      pair<int, char> p = *t.find_by_order(d - 1);
      char e = (p.second - 'A' + c) % 26 + 'A';
      t.erase(p);
      --m[e];
      (c += m[e]) %= 26;
      map<char, int> x;
      each (i, m) {
        if (i.second) x[(i.first - 'A' + m[e]) % 26 + 'A'] = i.second;
      }
      m = x;
    }
    cout << z << endl;
  }

  return 0;
}