#ifdef DEBUG #define _GLIBCXX_DEBUG #else #pragma GCC optimize ( "O3" ) #pragma GCC optimize( "unroll-loops" ) #pragma GCC target ( "sse4.2,fma,avx2,popcnt,lzcnt,bmi2" ) #endif #include using namespace std; using ll = long long; #define TYPE_OF( VAR ) remove_const::type >::type #define UNTIE ios_base::sync_with_stdio( false ); cin.tie( nullptr ) #define CEXPR( LL , BOUND , VALUE ) constexpr const LL BOUND = VALUE #define CIN( LL , A ) LL A; cin >> A #define ASSERT( A , MIN , MAX ) assert( ( MIN ) <= A && A <= ( MAX ) ) #define CIN_ASSERT( A , MIN , MAX ) CIN( TYPE_OF( MAX ) , A ); ASSERT( A , MIN , MAX ) #define FOR( VAR , INITIAL , FINAL_PLUS_ONE ) for( TYPE_OF( FINAL_PLUS_ONE ) VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) #define FOREQ( VAR , INITIAL , FINAL ) for( TYPE_OF( FINAL ) VAR = INITIAL ; VAR <= FINAL ; VAR ++ ) #define FOREQINV( VAR , INITIAL , FINAL ) for( TYPE_OF( INITIAL ) VAR = INITIAL ; VAR >= FINAL ; VAR -- ) #define FOR_ITR( ARRAY , ITR , END ) for( auto ITR = ARRAY .begin() , END = ARRAY .end() ; ITR != END ; ITR ++ ) #define REPEAT( HOW_MANY_TIMES ) FOR( VARIABLE_FOR_REPEAT , 0 , HOW_MANY_TIMES ) #define QUIT return 0 #define COUT( ANSWER ) cout << ( ANSWER ) << "\n" #define RETURN( ANSWER ) COUT( ANSWER ); QUIT template class PrimeEnumeration { public: INT m_val[length_max]; int m_length; inline constexpr PrimeEnumeration(); }; template inline constexpr PrimeEnumeration::PrimeEnumeration() : m_val() , m_length( 0 ) { bool is_comp[val_limit] = {}; for( INT i = 2 ; i < val_limit ; i++ ){ if( is_comp[i] == false ){ INT j = i; while( ( j += i ) < val_limit ){ is_comp[j] = true; } m_val[m_length++] = i; if( m_length >= length_max ){ break; } } } } // n < val_limitの2乗 の時のみサポート。 template list EnumerateDivisor( const PrimeEnumeration& prime , INT n ) noexcept { list > factor{}; for( int i = 0 ; i < prime.m_length ; i++ ){ const INT& pi = prime.m_val[i]; int ei = 0; while( n % pi == 0 ){ n /= pi; ei++; } if( ei > 0 ){ factor.push_back( pair( pi , ei ) ); } if( n == 1 ){ break; } } if( n > 1 ){ factor.push_back( pair( n , 1 ) ); } list divisor{}; divisor.push_back( 1 ); auto begin = divisor.begin() , end = divisor.end(); while( ! factor.empty() ){ pair& factor_curr = factor.front(); INT& pi = factor_curr.first; int& ei = factor_curr.second; list temp{}; INT power = 1; for( int e = 1 ; e <= ei ; e++ ){ power *= pi; for( auto itr = begin ; itr != end ; itr++ ){ temp.push_back( *itr * power ); } } while( ! temp.empty() ){ divisor.push_back( temp.front() ); temp.pop_front(); } factor.pop_front(); } return divisor; } int main() { UNTIE; CEXPR( int , bound , 100000 ); CIN_ASSERT( N , 1 , bound ); CEXPR( int , sqrt_bound , 317 ); constexpr PrimeEnumeration prime{}; int count[bound+1] = {}; REPEAT( N ){ CIN_ASSERT( A , 1 , bound ); int& count_A = count[A]; list divisor = EnumerateDivisor( prime , A ); int count_curr = 0; while( ! divisor.empty() ){ int& count_d = count[divisor.front()]; count_d < count_curr ? count_curr : count_curr = count_d + 1; divisor.pop_front(); } count_A < count_curr ? count_A = count_curr : count_A; } int answer = 0; FOREQ( i , 1 , bound ){ int& count_i = count[i]; answer < count_i ? answer = count_i : answer; } RETURN( answer ); }