#include <bits/stdc++.h>
using namespace std;
const int MAXN = (int)2e5 + 10, L = 4, INF = (int)1e9;
struct State {
  int fa, len, tr[L], w[L];
} SAM[MAXN];
char t[MAXN];
vector<int> l[MAXN];
int m, tot;
unsigned long long a[L], b[L][L], c[L][L];
unsigned long long n;
int Build(int pre, int id) {
  int cp = ++tot;
  SAM[cp].len = SAM[pre].len + 1;
  for (; !SAM[pre].tr[id] && pre; SAM[pre].tr[id] = cp, pre = SAM[pre].fa)
    ;
  if (pre)
    if (SAM[pre].len + 1 == SAM[SAM[pre].tr[id]].len)
      SAM[cp].fa = SAM[pre].tr[id];
    else {
      int tp = SAM[pre].tr[id];
      ++tot, SAM[tot].len = SAM[pre].len + 1, SAM[tot].fa = SAM[tp].fa;
      memcpy(SAM[tot].tr, SAM[tp].tr, sizeof(SAM[tot].tr));
      SAM[cp].fa = SAM[tp].fa = tot;
      for (; pre && SAM[pre].tr[id] == tp;
           SAM[pre].tr[id] = tot, pre = SAM[pre].fa)
        ;
    }
  else
    SAM[cp].fa = 1;
  return cp;
}
void init() {
  cin >> n;
  scanf("%s", t + 1);
  m = strlen(t + 1);
  tot = 1;
  for (int i = 1, p = 1; i <= m; ++i) p = Build(p, t[i] - 'A');
  for (int i = 1; i <= tot; ++i) {
    for (int j = 0; j < L; ++j)
      if (!SAM[i].tr[j])
        SAM[i].w[j] = 1;
      else
        SAM[i].w[j] = INF;
    l[SAM[i].len].push_back(i);
  }
  for (int i = m; i >= 0; --i)
    for (int j = 0; j < (int)l[i].size(); ++j)
      for (int k = 0; k < L; ++k)
        if (SAM[l[i][j]].tr[k])
          for (int p = 0; p < L; ++p) {
            int first = l[i][j];
            SAM[first].w[p] =
                min(SAM[first].w[p], SAM[SAM[first].tr[k]].w[p] + 1);
          }
}
void mul(unsigned long long a[][L], unsigned long long b[][L],
         unsigned long long c[][L]) {
  static unsigned long long w[L][L];
  for (int i = 0; i < L; ++i)
    for (int j = 0; j < L; ++j) w[i][j] = n + 1;
  for (int i = 0; i < L; ++i)
    for (int j = 0; j < L; ++j)
      for (int k = 0; k < L; ++k) w[i][j] = min(w[i][j], b[i][k] + c[k][j]);
  for (int i = 0; i < L; ++i)
    for (int j = 0; j < L; ++j) a[i][j] = w[i][j];
}
void Pow(unsigned long long a[][L], unsigned long long b) {
  static unsigned long long d[L][L];
  for (int i = 0; i < L; ++i)
    for (int j = 0; j < L; ++j) d[i][j] = n + 1;
  for (int i = 0; i < L; ++i) d[i][i] = 0;
  for (; b; mul(a, a, a), b /= 2)
    if (b & 1) mul(d, d, a);
  memcpy(a, d, sizeof(d));
}
unsigned long long check(unsigned long long k) {
  memcpy(b, c, sizeof(b));
  Pow(b, k - 2);
  unsigned long long Tohka = n + 1;
  for (int i = 0; i < L; ++i)
    for (int j = 0; j < L; ++j) Tohka = min(Tohka, a[i] + b[i][j]);
  return Tohka;
}
unsigned long long Find(unsigned long long l, unsigned long long r) {
  while (l <= r) {
    unsigned long long mid = (l + r) >> 1;
    if (check(mid) > n)
      r = mid - 1;
    else
      l = mid + 1;
  }
  return r;
}
void solve() {
  for (int i = 0; i < L; ++i) a[i] = max(SAM[1].w[i], 1);
  for (int i = 0; i < L; ++i)
    for (int j = 0; j < L; ++j) c[i][j] = max(SAM[SAM[1].tr[i]].w[j], 1);
  if (n == 1)
    puts("1");
  else
    cout << Find(2, n) << endl;
}
int main() {
  init();
  solve();
  fclose(stdin);
  fclose(stdout);
  return 0;
}
