#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using namespace placeholders; using LL = long long; using ULL = unsigned long long; using VI = vector< int >; using VVI = vector< vector< int > >; using VS = vector< string >; using ISS = istringstream; using OSS = ostringstream; using PII = pair< int, int >; using VPII = vector< pair< int, int > >; template < typename T = int > using VT = vector< T >; template < typename T = int > using VVT = vector< vector< T > >; template < typename T = int > using LIM = numeric_limits< T >; template < typename T > inline istream& operator>>( istream &s, vector< T > &v ){ for ( T &t : v ) { s >> t; } return s; } template < typename T > inline ostream& operator<<( ostream &s, const vector< T > &v ){ for ( int i = 0; i < int( v.size() ); ++i ){ s << ( " " + !i ) << v[i]; } return s; } void in_impl(){}; template < typename T, typename... TS > void in_impl( T &head, TS &... tail ){ cin >> head; in_impl( tail ... ); } #define IN( T, ... ) T __VA_ARGS__; in_impl( __VA_ARGS__ ); template < typename T > struct getv_fmt; template <> struct getv_fmt< int >{ static constexpr const char *fmt = "%d"; }; template <> struct getv_fmt< long long >{ static constexpr const char *fmt = "%lld"; }; template < typename T > void getv( std::vector< T > &v ){ for_each( begin( v ), end( v ), []( T &a ){ scanf( getv_fmt< T >::fmt, &a ); } ); }; template < typename T > inline T fromString( const string &s ) { T res; istringstream iss( s ); iss >> res; return res; } template < typename T > inline string toString( const T &a ) { ostringstream oss; oss << a; return oss.str(); } #define NUMBERED( name, number ) NUMBERED2( name, number ) #define NUMBERED2( name, number ) name ## _ ## number #define REP1( n ) REP2( NUMBERED( REP_COUNTER, __LINE__ ), n ) #define REP2( i, n ) REP3( i, 0, n ) #define REP3( i, m, n ) for ( int i = ( int )( m ); i < ( int )( n ); ++i ) #define GET_REP( a, b, c, F, ... ) F #define REP( ... ) GET_REP( __VA_ARGS__, REP3, REP2, REP1 )( __VA_ARGS__ ) #define FOR( e, c ) for ( auto &&e : c ) #define ALL( c ) begin( c ), end( c ) #define AALL( a ) ( remove_all_extents< decltype( a ) >::type * )a, ( remove_all_extents< decltype( a ) >::type * )a + sizeof( a ) / sizeof( remove_all_extents< decltype( a ) >::type ) #define DRANGE( c, p ) begin( c ), begin( c ) + ( p ), end( c ) #define SZ( v ) ( (int)( v ).size() ) #define EXIST( c, e ) ( ( c ).find( e ) != ( c ).end() ) template < typename T > inline bool chmin( T &a, const T &b ){ if ( b < a ) { a = b; return true; } return false; } template < typename T > inline bool chmax( T &a, const T &b ){ if ( a < b ) { a = b; return true; } return false; } #define PB push_back #define EM emplace #define EB emplace_back #define BI back_inserter #define MP make_pair #define fst first #define snd second #define DUMP( x ) cerr << #x << " = " << ( x ) << endl constexpr int MOD = 1000000007; // a^x を mod で求める // 反復二乗法 // O( log x ) long long mod_pow( long long a, long long x, long long mod ) { a %= mod; long long res = 1; for ( ; x; x >>= 1, ( a *= a ) %= mod ) { if ( x & 1 ) { ( res *= a ) %= mod; } } return res; } // p が素数のとき、p を法とする剰余体での逆元を求める // Fermat の小定理を利用 // a^{ p - 1 } \equiv 1 ( mod p ) // a^{ p - 2 } \equiv a^{-1} ( mod p ) // incluide : mod_pow int mod_inverse( long long a, long long p ) { return mod_pow( a, p - 2, p ); } struct SubstrEquivalence { const int L; VT< LL > hashes, psum, base_pow, base_pow_i; SubstrEquivalence( const string S ) : L( SZ( S ) ), hashes( L ), psum( 1 ), base_pow( 1, 1 ) { constexpr LL B = 999999937; REP( i, L ) { base_pow.PB( base_pow.back() * B % MOD ); } transform( ALL( base_pow ), BI( base_pow_i ), [&]( const LL a ){ return mod_inverse( a, MOD ); } ); REP( i, L ) { hashes[i] = base_pow[i] * S[i] % MOD; } partial_sum( ALL( hashes ), BI( psum ) ); transform( ALL( psum ), begin( psum ), bind( modulus< LL >(), _1, MOD ) ); return; } LL hash( const int a, const int b ) { const LL m = ( ( psum[b] - psum[a] ) % MOD + MOD ) % MOD; return m * base_pow_i[a] % MOD; } bool equiv( const int a, const int b, const int c, const int d ) { return hash( a, b ) == hash( c, d ); } }; int main() { cin.tie( 0 ); ios::sync_with_stdio( false ); cout << setprecision( 12 ) << fixed; IN( string, S ); const int L = SZ( S ); SubstrEquivalence strequiv( S ); int dp[ 1 << 13 ]; dp[0] = 1; const int l2 = ( L + 1 ) / 2; REP( i, l2 ) { for ( int j = 1; i + j <= L; ++j ) { const int p = i, q = L - i - j; if ( ( p == q || p + j <= q ) && strequiv.equiv( p, p + j, q, q + j ) ) { ( dp[ min( l2, i + j ) ] += dp[i] ) %= MOD; } } } cout << dp[ l2 ] << endl; return 0; }