#include using namespace std; typedef unsigned long long ull; typedef long long ll; typedef pair pii; typedef pair pll; typedef pair pdd; typedef vector vl; typedef vector> vvl; //typedef vector> Graph; const ll mod = 1e9 + 7; //const ll mod = 998244353; #define REP(i,n) for(ll i=0;i<(ll)n;i++) #define dump(x) cerr << #x << " = " << (x) << endl; #define spa << " " << #define fi first #define se second template bool chmax(T &a, const T &b) { if (a bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; } template ostream& operator << (ostream& os, const pair v){ os << "(" << v.first << ", " << v.second << ")"; return os; } template ostream& operator << (ostream& os, const vector v){ for(int i = 0; i < (int)v.size(); i++){if(i > 0){os << " ";} os << v[i];} return os; } template ostream& operator << (ostream& os, const vector> v){ for(int i = 0; i < (int)v.size(); i++){if(i > 0){os << endl;} os << v[i];} return os; } template void debug(vector>&v,ll h,ll w){for(ll i=0;i void debug(vector&v,ll n){if(n!=0)cerr< class modint { // long long から modint を作るときは必ず正の数にしてからコンストラクタに入れること! // そうしないとバグります using u64 = std::uint_fast64_t; public: u64 a; constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {} constexpr u64 &value() noexcept { return a; } constexpr const u64 &value() const noexcept { return a; } constexpr modint operator+(const modint rhs) const noexcept { return modint(*this) += rhs; } constexpr modint operator-(const modint rhs) const noexcept { return modint(*this) -= rhs; } constexpr modint operator*(const modint rhs) const noexcept { return modint(*this) *= rhs; } constexpr modint operator/(const modint rhs) const noexcept { return modint(*this) /= rhs; } constexpr modint &operator+=(const modint rhs) noexcept { a += rhs.a; if (a >= Modulus) { a -= Modulus; } return *this; } constexpr modint &operator-=(const modint rhs) noexcept { if (a < rhs.a) { a += Modulus; } a -= rhs.a; return *this; } constexpr modint &operator*=(const modint rhs) noexcept { a = a * rhs.a % Modulus; return *this; } constexpr modint &operator/=(modint rhs) noexcept { u64 exp = Modulus - 2; while (exp) { if (exp % 2) { *this *= rhs; } rhs *= rhs; exp /= 2; } return *this; } }; using mint = modint; using vm = vector; using vvm = vector; ostream& operator << (ostream& os, const mint v){ os << v.value(); return os; } template constexpr T power(T x, U exp) { T ret = static_cast(1); while (exp) { if (exp % static_cast(2) == static_cast(1)) ret *= x; exp /= static_cast(2); x *= x; } return ::std::move(ret); } int main(){ cin.tie(0); ios::sync_with_stdio(false); string S; cin >> S; mint res = 0; ll N = S.size(); vvm dp1(N+1, vm(27, 0)); vvm dp2(N+1, vm(27, 0)); dp1[0][0] = 1; REP(i, N){ res *= 2; ll idx = S[i]-'a'+1; dp1[i+1][0] = 1; dp1[i+1][idx] += 1; for(int j=1;j<27;j++){ dp1[i+1][j] += dp1[i][j]; dp1[i+1][idx] += dp1[i][j]; if(idx != j){ res += dp1[i][j]; } } } res += power(mint(2), N); res += (mod-1); cout << res << endl; return 0; }