#pragma GCC optimize ("O3") #pragma GCC target ("avx") #include "bits/stdc++.h" // define macro "/D__MAI" using namespace std; typedef long long int ll; #define xprintf(fmt,...) fprintf(stderr,fmt,__VA_ARGS__) #define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:v){cout< ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout< ostream& operator <<(ostream &o, const pair p) { o << "(" << p.first << ":" << p.second << ")"; return o; } template inline size_t argmin(iterator begin, iterator end) { return distance(begin, min_element(begin, end)); } template inline size_t argmax(iterator begin, iterator end) { return distance(begin, max_element(begin, end)); } template T& maxset(T& to, const T& val) { return to = max(to, val); } template T& minset(T& to, const T& val) { return to = min(to, val); } void bye(string s, int code = 0) { cout << s << endl; exit(0); } mt19937_64 randdev(8901016); inline ll rand_range(ll l, ll h) { return uniform_int_distribution(l, h)(randdev); } #ifdef __MAI #define getchar_unlocked getchar #define putchar_unlocked putchar #endif #ifdef __VSCC #define getchar_unlocked _getchar_nolock #define putchar_unlocked _putchar_nolock #endif namespace { #define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E) class MaiScanner { public: template void input_integer(T& var) { var = 0; T sign = 1; int cc = getchar_unlocked(); for (; cc<'0' || '9'>(int& var) { input_integer(var); return *this; } inline MaiScanner& operator>>(long long& var) { input_integer(var); return *this; } inline MaiScanner& operator>>(string& var) { int cc = getchar_unlocked(); for (; !isvisiblechar(cc); cc = getchar_unlocked()); for (; isvisiblechar(cc); cc = getchar_unlocked()) var.push_back(cc); return *this; } template void in(IT begin, IT end) { for (auto it = begin; it != end; ++it) *this >> *it; } }; } MaiScanner scanner; namespace std { template class hash> { public: size_t operator()(const pair& x) const { return hash()(x.first) ^ hash()(x.second); } }; } class rollinghash { typedef unsigned long long rh_t; static const rh_t MD_1 = (rh_t)(1e9 + 21); static const rh_t PW = (rh_t)(1e9 + 7); static vector pow_table[2]; public: vector hashes[2]; rollinghash() {} rollinghash(const string& s) { build(s); } inline pair operator()(int begin, int end) { return pair( (hashes[0][end] - hashes[0][begin] * pow_table[0][end - begin]), (hashes[1][end] - (hashes[1][begin] * pow_table[1][end - begin]) % MD_1 + MD_1) % MD_1 ); } void build_pow(size_t size) { ++size; if (pow_table[0].size() < size) { pow_table[0].reserve(size); pow_table[1].reserve(size); if (pow_table[0].empty()) pow_table[0].push_back(1), pow_table[1].push_back(1); for (size_t i = pow_table[0].size(); i < size; ++i) { pow_table[0].push_back(pow_table[0].back() * PW); pow_table[1].push_back(pow_table[1].back() * PW%MD_1); } } } void build(const string& src) { size_t m = src.size() + 1; build_pow(m); hashes[0].resize(m); hashes[1].resize(m); hashes[0][0] = hashes[1][0] = 0; for (size_t i = 1; i < m; ++i) { rh_t c = src[i - 1]; hashes[0][i] = hashes[0][i - 1] * PW + c; hashes[1][i] = (hashes[1][i - 1] * PW + c)%MD_1; } } }; vector rollinghash::pow_table[2]; ll m, n, kei; string str; rollinghash rh; unordered_map memo; inline bool my_same(int left, int right, int k) { return rh(left,left+k) == rh(right-k,right); } ll dfs(int left, int right) { if (right - left <= 1) return 1; ll key = (right << 32) | left; if (memo.count(key)) return memo[key]; // + [left,right]を1つのブロック // + [left,left+k],[right-k,right] で1つのpair ll ans = 1; for (int k = 1; left + k <= right - k; ++k) { //cout << " " << make_pair(left + k, right - k) << endl; if (my_same(left, right, k)) ans = (ans + dfs(left + k, right - k)) % MD; } //cout << make_pair(left,right)<> str; n = str.size(); rh.build(str); ll ans = dfs(0, n); cout << ans << endl; return 0; }