#include #define rep(i,a,b) for(int i=a;i=b;i--) #define fore(i,a) for(auto &i:a) #pragma GCC optimize ("-O3") using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); } //--------------------------------------------------------------------------------------------------- template struct ModInt { static const int Mod = MOD; unsigned x; ModInt() : x(0) { } ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; } ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; } int get() const { return (int)x; } ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; } ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; } ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; } ModInt &operator/=(ModInt that) { return *this *= that.inverse(); } ModInt operator+(ModInt that) const { return ModInt(*this) += that; } ModInt operator-(ModInt that) const { return ModInt(*this) -= that; } ModInt operator*(ModInt that) const { return ModInt(*this) *= that; } ModInt operator/(ModInt that) const { return ModInt(*this) /= that; } ModInt inverse() const { long long a = x, b = MOD, u = 1, v = 0; while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); } return ModInt(u); } bool operator==(ModInt that) const { return x == that.x; } bool operator!=(ModInt that) const { return x != that.x; } ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; } }; template ostream& operator<<(ostream& st, const ModInt a) { st << a.get(); return st; }; template ModInt operator^(ModInt a, unsigned long long k) { ModInt r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r; } typedef ModInt<1000000007> mint; typedef ModInt<1000000007> mint1; typedef ModInt<1000000009> mint2; int getrand(int l, int r) { // [l, r] static uint32_t y = time(NULL); y ^= (y << 13); y ^= (y >> 17); y ^= (y << 5); return y % (r - l + 1) + l; } struct RollingHash { int primes[10] = { 10007, 10009, 10037, 10039, 10061, 10067, 10069, 10079, 10091, 10093 }; mint1 p1; mint2 p2; int n; vector m1; vector m2; vector v1; vector v2; RollingHash() { rep(i, 0, 101) { int a = getrand(0, 9); int b = getrand(0, 9); swap(primes[a], primes[b]); } p1 = primes[0], p2 = primes[1]; } void init(string s, char o = 'a') { vector v; fore(c, s) v.push_back(c - o); init(v); } void init(vector s) { n = s.size(); m1.resize(n); m2.resize(n); v1.resize(n); v2.resize(n); m1[0] = 1; m2[0] = 1; v1[0] = s[0]; v2[0] = s[0]; rep(i, 1, n) { m1[i] = m1[i - 1] * p1; m2[i] = m2[i - 1] * p2; v1[i] = v1[i - 1] + m1[i] * s[i]; v2[i] = v2[i - 1] + m2[i] * s[i]; } } inline pair hash(int l, int r) { // s[l..r] assert(l <= r); assert(r < n); mint1 a = v1[r]; if (l) a -= v1[l - 1]; a *= m1[n - 1 - r]; mint2 b = v2[r]; if (l) b -= v2[l - 1]; b *= m2[n - 1 - r]; return { a, b }; } }; /*---------------------------------------------------------------------------------------------------             ∧_∧       ∧_∧  (´<_` )  Welcome to My Coding Space!      ( ´_ゝ`) /  ⌒i     /   \    | |     /   / ̄ ̄ ̄ ̄/  |   __(__ニつ/  _/ .| .|____      \/____/ (u ⊃ ---------------------------------------------------------------------------------------------------*/ string S; int N; RollingHash rh; //--------------------------------------------------------------------------------------------------- mint memo[10101]; int vis[10101]; mint f(int L, int R) { if (vis[L]) return memo[L]; mint res = 1; if (L == R) res = 1; else if (L + 1 == R) { if (S[L] == S[R]) res = 2; else res = 1; } else { int l = L + 1, r = R - 1; if (L + 1 == R) { if (S[L] == S[R]) res += 1; } while (l <= r) { if (rh.hash(L, l - 1) == rh.hash(r + 1, R)) res += f(l, r); l++; r--; } } vis[L] = 1; return memo[L] = res; } //--------------------------------------------------------------------------------------------------- void _main() { cin >> S; N = S.length(); rh.init(S); cout << f(0, N - 1) << endl; }