#include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using lint = long long; constexpr int MOD = 1000000007, INF = 1010101010; constexpr lint LINF = 1LL << 60; template ostream &operator<<(ostream &os, const vector &vec) { for (const auto &e : vec) os << e << (&e == &vec.back() ? "" : " "); return os; } #ifdef _DEBUG template void dump(const char* str, T &&h) { cerr << str << " = " << h << "\n"; }; template void dump(const char* str, Head &&h, Tail &&... t) { while (*str != ',') cerr << *str++; cerr << " = " << h << "\n"; dump(str + (*(str + 1) == ' ' ? 2 : 1), t...); } #define DMP(...) dump(#__VA_ARGS__, __VA_ARGS__) #else #define DMP(...) ((void)0) #endif template struct Mint { lint val; constexpr Mint(lint v = 0) noexcept : val(v % Modulo) { if (val < 0) v += Modulo; } constexpr Mint& operator += (const Mint &r) noexcept { val += r.val; if (val >= Modulo) val -= Modulo; return *this; } constexpr Mint& operator -= (const Mint &r) noexcept { val -= r.val; if (val < 0) val += Modulo; return *this; } constexpr Mint& operator *= (const Mint &r) noexcept { val = val * r.val % Modulo; return *this; } constexpr Mint& operator /= (const Mint &r) noexcept { lint a = r.val, b = Modulo, u = 1, v = 0; while (b) { lint t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); } val = val * u % Modulo; if (val < 0) val += Modulo; return *this; } constexpr Mint operator + (const Mint &r) const noexcept { return Mint(*this) += r; } constexpr Mint operator - (const Mint &r) const noexcept { return Mint(*this) -= r; } constexpr Mint operator * (const Mint &r) const noexcept { return Mint(*this) *= r; } constexpr Mint operator / (const Mint &r) const noexcept { return Mint(*this) /= r; } constexpr int getmod() { return Modulo; } constexpr Mint operator - () const noexcept { return val ? Modulo - val : 0; } constexpr bool operator == (const Mint &r) const noexcept { return val == r.val; } constexpr bool operator != (const Mint &r) const noexcept { return val != r.val; } friend ostream &operator << (ostream &os, const Mint &x) noexcept { return os << x.val; } friend istream &operator >> (istream &is, Mint &x) noexcept { lint tmp; is >> tmp; x = Mint(tmp); return is; } friend constexpr Mint modpow(const Mint &a, lint n) noexcept { Mint res(1), tmp = a; while (n > 0) { if (n & 1) res *= tmp; tmp *= tmp; n >>= 1; } return res; } }; //// mod, base from https://gist.github.com/privet-kitty/295ac9202b7abb3039b493f8238bf40f class RollingHash { private: using Mint1 = Mint<2147483647>; using Mint2 = Mint<2147483629>; vector hash1, pow1; vector hash2, pow2; const int base1 = 2147483634; const int base2 = 2147483627; int sz; public: RollingHash() {} RollingHash(const string &s) :sz(s.size()) { hash1.assign(sz + 1, 0); pow1.assign(sz + 1, 1); hash2.assign(sz + 1, 0); pow2.assign(sz + 1, 1); for (int i = 0; i < sz; i++) { hash1[i + 1] = hash1[i] * base1 + s[i]; pow1[i + 1] = pow1[i] * base1; hash2[i + 1] = hash2[i] * base2 + s[i]; pow2[i + 1] = pow2[i] * base2; } } pair get(int l, int r) { int res1 = (hash1[r] - hash1[l] * pow1[r - l]).val; int res2 = (hash2[r] - hash2[l] * pow2[r - l]).val; return { res1, res2 }; } }; int main() { cin.tie(nullptr); ios::sync_with_stdio(false); string S; cin >> S; int sz = S.size(); RollingHash rh(S); using mint = Mint; vector dp(sz / 2 + 1, 0); dp[0] = 1; for (int i = 1; i <= sz / 2; i++) { for (int j = 1; j <= i; j++) { if (rh.get(i - j, i) == rh.get(sz - i, sz - (i - j))) { dp[i] += dp[i - j]; } } } mint ans = 0; for (int i = 0; i < sz / 2 + 1; i++) ans += dp[i]; cout << ans << "\n"; return 0; }