//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,avx512f")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <stack>
#include <queue>
#include <bitset>
#include <numeric>
#include <cassert>
#include <memory>
#include <random>
#include <functional>
#include <complex>
#include <immintrin.h>
#include <stdexcept>
#ifdef DEBUG
#include "./CompetitiveProgrammingCpp/debug.hpp"
#include "./CompetitiveProgrammingCpp/Timer.hpp"
#include "./CompetitiveProgrammingCpp/sample.hpp"
#else
#define dump(...)
#endif

/* macro */
#define FOR(i, b, e) for(ll i = (ll)(b); i < (ll)(e); ++i)
#define RFOR(i, b, e) for(ll i = (ll)((e)-1); i >= (ll)(b); --i)
#define REP(i, n) FOR(i, 0, (n))
#define RREP(i, n) RFOR(i, 0, (n))
#define REPC(x,c) for(const auto& x:(c))
#define REPI2(it,b,e) for(auto it = (b); it != (e); ++it)
#define REPI(it,c) REPI2(it, (c).begin(), (c).end())
#define RREPI(it,c) REPI2(it, (c).rbegin(), (c).rend())
#define REPI_ERACE2(it, b, e) for(auto it = (b); it != (e);)
#define REPI_ERACE(it, c) REPI_ERACE2(it, (c).begin(), (c).end())
#define ALL(x) (x).begin(),(x).end()
#define cauto const auto&
/* macro func */
template<class T>
inline auto sort(T& t) { std::sort(ALL(t)); }
template<class T>
inline auto rsort(T& t) { std::sort((t).rbegin(), (t).rend()); }
template<class T>
inline auto unique(T& t) { (t).erase(unique((t).begin(), (t).end()), (t).end()); }
template<class T, class S>
inline auto chmax(T& t, const S& s) { if(s > t) { t = s; return true; } return false; }
template<class T, class S>
inline auto chmin(T& t, const S& s) { if(s < t) { t = s; return true; } return false; }
inline auto BR() { std::cout << "\n"; }

/* type define */
using ll = long long;
using VS = std::vector<std::string>;
using VL = std::vector<long long>;
using VVL = std::vector<VL>;
using VVVL = std::vector<VVL>;
using VVVVL = std::vector<VVVL>;
using VVVVVL = std::vector<VVVVL>;
using VD = std::vector<double>;
template<class T>
using V = std::vector<T>;
template<class T = ll, class U = T>
using P = std::pair<T, U>;
using PAIR = P<ll>;

/* using std */
using std::cout;
constexpr char endl = '\n';
using std::cin;
using std::pair;
using std::string;
using std::stack;
using std::queue;
using std::deque;
using std::vector;
using std::list;
using std::map;
using std::unordered_map;
using std::multimap;
using std::unordered_multimap;
using std::set;
using std::unordered_set;
using std::unordered_multiset;
using std::multiset;
using std::bitset;
using std::priority_queue;

/* Initial processing  */
struct Preprocessing { Preprocessing() { std::cin.tie(0); std::ios::sync_with_stdio(0); }; }_Preprocessing;

/* Remove the source of the bug */
auto pow(signed, signed) { assert(false); }

/* define hash */
namespace std {
template <>	class hash<std::pair<ll, ll>> { public:	size_t operator()(const std::pair<ll, ll>& x) const { return hash<ll>()(1000000000 * x.first + x.second); } };
}

/* input */
template<class T> std::istream& operator >> (std::istream& is, vector<T>& vec) { for(T& x : vec) is >> x; return is; }

/* constant value */
constexpr ll MOD = 1000000007;
// constexpr ll MOD = 998244353;

//=============================================================================================

auto solve_c(ll n, const string& s) ->ll {
    ll c1 = 0;
    string agct = "AGCT";
    REPC(c, s) REPC(t, agct)if(c == t) { ++c1; }
    if(c1 == 0) { return 0LL; }

    char p = s[c1 - 1];
    ll c2 = -1;
    REPC(c, s)if(c == p) { ++c2; }

    string t = "";
    REP(i, n) if(i != c1 - 1) {
        ll k = (s[i] + c2 - 'A') % 26;
        t += ('A' + k);
    }
    return 1LL + solve_c(n - 1, t);
}

template<class T>
class isMonoid {
    template <class U>
    static auto check(U x) -> decltype(x.binaryOperation(x), std::true_type{});
    static std::false_type check(...);
public:
    static bool const value = decltype(check(std::declval<T>()))::value;
};

template<class Monoid, std::enable_if_t<isMonoid<Monoid>::value, std::nullptr_t> = nullptr >
class SegmentTree {
private:
    const int m_size;
    vector<Monoid> m_node;

    int calcSize(int n) const { int size = 1; while(size < n) { size <<= 1; }return size; }

    auto _query(int a, int b) {
        return _query(a, b + 1, 0, 0, m_size);
    }
    auto _query(int a, int b, int k, int l, int r) {
        if(r <= a || b <= l) { return Monoid(); }
        if(a <= l && r <= b) { return m_node[k]; }
        return _query(a, b, 2 * k + 1, l, (l + r) / 2).binaryOperation(
            _query(a, b, 2 * k + 2, (l + r) / 2, r)
        );
    }
public:
    SegmentTree(int n) : m_size(calcSize(n)), m_node(m_size * 2 - 1) {}

    auto add(int itr, Monoid&& val) {
        int i = itr + m_size - 1;
        m_node[i] = std::forward<decltype(val)>(val);
        while(i > 0) {
            i = (i - 1) / 2;
            m_node[i] = m_node[i * 2 + 1].binaryOperation(m_node[i * 2 + 2]);
        }
    }
    auto query(int a, int b, int k, int l, int r) { return _query(a, b, k, l, r).m_val; }
    auto query(int a, int b) { return query(a, b + 1, 0, 0, m_size); }
};


template<
    class S,   // 要素の型
    S element, // 元
    class T // lambdaはC++20じゃないと渡せなかった．．．
    // S T(S, S)  // 2項演算子
>
struct Monoid {
    S m_val;
    Monoid() :m_val(element) {}
    Monoid(S val) :m_val(val) {}
    Monoid binaryOperation(const Monoid& m2)const { return T()(m_val, m2.m_val); }
};


template <class Lambda>
auto binarySearch(ll mn, ll mx, const Lambda& judge, bool rev = false) {
    auto ok = mx;
    auto ng = mn - 1;
    while(ok - ng > 1) {
        auto mid = (ok + ng) / 2;
        auto isOk = judge(mid);
        if((isOk && !rev) || (!isOk && rev)) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    return ok;
}

auto solve(ll n, const string& s) {
    VL agct{'A' - 'A','G' - 'A','C' - 'A','T' - 'A'};

    VL cnt(26);
    REPC(c, s) { ++cnt[c - 'A']; }
    struct Functor {
        auto operator()(ll a, ll b)const { return a + b; }
    };
    using M = Monoid<ll, 0, Functor>;
    auto tree = SegmentTree<M>(n);
    REP(i, n) { tree.add(i, 1); }

    ll rotate = 0;
    REP(i, n) {
        ll c1 = 0;
        REPC(x, agct) { c1 += cnt[(x - rotate + 26) % 26]; }
        if(c1 == 0) { return i; }

        ll it = binarySearch(0, n - 1, [&](ll mid) {
            return tree.query(0, mid) >= c1;
        });
        ll c = s[it] - 'A';
        --cnt[c];
        tree.add(it, 0);

        ll c2 = cnt[c];
        (rotate += c2) %= 26;

        char d = (c + rotate - c2 + 26) % 26 + 'A';
        // dump(c1, c2, d);
    }
    return n;
}

signed main() {
    ll n;
    cin >> n;
    string s;
    cin >> s;

    auto ans = solve(n, s);
    cout << ans << endl;

}