#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
using ll = long long int;
const ll MD = 1000000007ll;
const long double PI = 3.1415926535897932384626433832795L;
inline void assert_call(bool assertion, function<void()> f) {
  if (!assertion) {
    cerr << "assertion fault:" << endl;
    f();
    abort();
  }
}
template <typename T1, typename T2>
inline ostream& operator<<(ostream& o, const pair<T1, T2> p) {
  o << '(' << p.first << ':' << p.second << ')';
  return o;
}
template <typename Vec>
inline ostream& _ostream_vecprint(ostream& os, const Vec& a) {
  os << '[';
  for (const auto& e : a) os << ' ' << e << ' ';
  os << ']';
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& o, const vector<T>& v) {
  return _ostream_vecprint(o, v);
}
template <typename T, size_t S>
inline ostream& operator<<(ostream& o, const array<T, S>& v) {
  return _ostream_vecprint(o, v);
}
template <typename T>
inline T& chmax(T& to, const T& val) {
  return to = max(to, val);
}
template <typename T>
inline T& chmin(T& to, const T& val) {
  return to = min(to, val);
}
void bye(string s, int code = 0) {
  cout << s << endl;
  exit(code);
}
mt19937_64 randdev(8901016);
template <typename T, typename Random = decltype(randdev),
          typename enable_if<is_integral<T>::value>::type* = nullptr>
inline T rand(T l, T h, Random& rand = randdev) {
  return uniform_int_distribution<T>(l, h)(rand);
}
template <typename T, typename Random = decltype(randdev),
          typename enable_if<is_floating_point<T>::value>::type* = nullptr>
inline T rand(T l, T h, Random& rand = randdev) {
  return uniform_real_distribution<T>(l, h)(rand);
}
class MaiScanner {
  FILE* fp_;

 public:
  inline MaiScanner(FILE* fp) : fp_(fp) {}
  template <typename T>
  void input_integer(T& var) noexcept {
    var = 0;
    T sign = 1;
    int cc = getc_unlocked(fp_);
    for (; cc < '0' || '9' < cc; cc = getc_unlocked(fp_))
      if (cc == '-') sign = -1;
    for (; '0' <= cc && cc <= '9'; cc = getc_unlocked(fp_))
      var = (var << 3) + (var << 1) + cc - '0';
    var = var * sign;
  }
  inline int c() noexcept { return getc_unlocked(fp_); }
  inline MaiScanner& operator>>(int& var) noexcept {
    input_integer<int>(var);
    return *this;
  }
  inline MaiScanner& operator>>(long long& var) noexcept {
    input_integer<long long>(var);
    return *this;
  }
  inline MaiScanner& operator>>(string& var) {
    int cc = getc_unlocked(fp_);
    for (; !(0x21 <= (cc) && (cc) <= 0x7E); cc = getc_unlocked(fp_))
      ;
    for (; (0x21 <= (cc) && (cc) <= 0x7E); cc = getc_unlocked(fp_))
      var.push_back(cc);
    return *this;
  }
  template <typename IT>
  inline void in(IT begin, IT end) {
    for (auto it = begin; it != end; ++it) *this >> *it;
  }
};
class MaiPrinter {
  FILE* fp_;

 public:
  inline MaiPrinter(FILE* fp) : fp_(fp) {}
  template <typename T>
  void output_integer(T var) noexcept {
    if (var == 0) {
      putc_unlocked('0', fp_);
      return;
    }
    if (var < 0) putc_unlocked('-', fp_), var = -var;
    char stack[32];
    int stack_p = 0;
    while (var) stack[stack_p++] = '0' + (var % 10), var /= 10;
    while (stack_p) putc_unlocked(stack[--stack_p], fp_);
  }
  inline MaiPrinter& operator<<(char c) noexcept {
    putc_unlocked(c, fp_);
    return *this;
  }
  inline MaiPrinter& operator<<(int var) noexcept {
    output_integer<int>(var);
    return *this;
  }
  inline MaiPrinter& operator<<(long long var) noexcept {
    output_integer<long long>(var);
    return *this;
  }
  inline MaiPrinter& operator<<(char* str_p) noexcept {
    while (*str_p) putc_unlocked(*(str_p++), fp_);
    return *this;
  }
  inline MaiPrinter& operator<<(const string& str) {
    const char* p = str.c_str();
    const char* l = p + str.size();
    while (p < l) putc_unlocked(*p++, fp_);
    return *this;
  }
  template <typename IT>
  void join(IT begin, IT end, char sep = ' ') {
    for (bool b = 0; begin != end; ++begin, b = 1)
      b ? *this << sep << *begin : *this << *begin;
  }
};
MaiScanner scanner(stdin);
MaiPrinter printer(stdout);
int N;
int last1, last2, pos1, pos2;
int main() {
  scanner >> N;
  int best = 0;
  for (auto i = decltype(N)(); (i) < (N); ++(i)) {
    int c;
    scanner >> c;
    if (last1 == 0) {
      last1 = c;
      pos1 = i;
    } else if (last2 == 0 && last1 != c) {
      last2 = c;
      pos2 = i;
      chmax(best, pos2 - pos1);
    } else {
      if (last1 != c) {
        chmax(best, i - pos1);
      }
      if (last2 != c) {
        chmax(best, i - pos2);
      }
    }
  }
  printer << best << '\n';
  return 0;
}
