We have a string of letters 'a' and 'b'. We want to perform some operations on it. On each step we choose one of substrings "ab" in the string and replace it with the string "bba". If we have no "ab" as a substring, our job is done. Print the minimum number of steps we should perform to make our job done modulo 109 + 7.

The string "ab" appears as a substring if there is a letter 'b' right after the letter 'a' somewhere in the string.

Input

The first line contains the initial string consisting of letters 'a' and 'b' only with length from 1 to 106.

Output

Print the minimum number of steps modulo 109 + 7.

Examples

Input

ab


Output

1


Input

aab


Output

3

Note

The first example: "ab"  →  "bba".

The second example: "aab"  →  "abba"  →  "bbaba"  →  "bbbbaa".
#include <bits/stdc++.h>
template <typename T>
struct ScanfSpecifier {};
template <>
struct ScanfSpecifier<char*> {
  static constexpr const char* value = "%s";
};
template <>
struct ScanfSpecifier<int> {
  static constexpr const char* value = "%d";
};
template <>
struct ScanfSpecifier<double> {
  static constexpr const char* value = "%lf";
};
template <>
struct ScanfSpecifier<float> {
  static constexpr const char* value = "%f";
};
template <>
struct ScanfSpecifier<char> {
  static constexpr const char* value = "%c";
};
template <>
struct ScanfSpecifier<const char*> {
  static constexpr const char* value = "%s";
};
template <>
struct ScanfSpecifier<unsigned long> {
  static constexpr const char* value = "%lu";
};
template <>
struct ScanfSpecifier<unsigned int> {
  static constexpr const char* value = "%u";
};
template <>
struct ScanfSpecifier<long long int> {
  static constexpr const char* value = "%lld";
};
template <typename T>
int RD(T& arg) {
  return std::scanf(ScanfSpecifier<T>::value, &arg);
}
template <int S>
int RD(char (&arg)[S]) {
  return std::scanf("%s", arg);
}
int RD(char* arg) { return std::scanf("%s", arg); }
template <>
int RD<char>(char& arg) {
  return std::scanf(" %c", &arg);
}
template <typename T, typename... Args>
int RD(T& arg1, Args&... args) {
  return RD(arg1) + RD(args...);
}
template <typename T>
T RD() {
  T ret;
  RD(ret);
  return ret;
}
template <typename It>
void RDV(It begin, It end) {
  while (begin != end) RD(*begin++);
}
template <typename C>
void RDV(C& c) {
  RDV(std::begin(c), std::end(c));
}
template <typename T>
void WT(T arg) {
  std::printf(ScanfSpecifier<T>::value, arg);
}
template <typename T, typename U>
void WT(std::pair<T, U> arg) {
  std::printf("(");
  WT(arg.first);
  std::printf(", ");
  WT(arg.second);
  std::printf(")");
}
template <typename... Args>
void WT(Args... args) {
  int alc = 0;
  int dummy[] = {((alc++ ? std::printf(" ") : 0), WT(args), 0)...};
}
template <typename... Args>
void WTL(Args... args) {
  WT(args...);
  std::printf("\n");
}
template <typename It>
void WTV(It begin, It end) {
  int alc = 0;
  while (begin != end) (alc++ ? std::printf(" ") : 0), WT(*begin++);
}
template <typename C>
void WTV(const C& c) {
  WTV(std::begin(c), std::end(c));
}
template <typename It>
void WTVL(It begin, It end) {
  WTV(begin, end);
  std::printf("\n");
}
template <typename C>
void WTVL(const C& c) {
  WTVL(std::begin(c), std::end(c));
}
template <unsigned int Z>
struct ZpZ {
  static const unsigned int P = Z;
  using U64 = unsigned long long int;
  U64 value;
  ZpZ(long long int n) {
    if (std::abs(n) >= P) n %= P;
    if (n < 0) n += P;
    value = n;
  }
  ZpZ() : value(0) {}
  ZpZ& operator+=(ZpZ p) {
    if ((value += p.value) >= P) value -= P;
    return *this;
  }
  ZpZ& operator-=(ZpZ p) {
    if (value >= p.value)
      value -= p.value;
    else
      value += P - p.value;
    return *this;
  }
  ZpZ& operator*=(ZpZ p) {
    value = value * p.value % P;
    return *this;
  }
  ZpZ& operator/=(ZpZ p) {
    value = value * p.inverse().value % P;
    return *this;
  }
  bool operator==(ZpZ p) { return value == p.value; }
  bool operator!=(ZpZ p) { return value != p.value; }
  ZpZ operator+(ZpZ r) const { return ZpZ(value) += r; }
  ZpZ operator-(ZpZ r) const { return ZpZ(value) -= r; }
  ZpZ operator*(ZpZ r) const { return ZpZ(value) *= r; }
  ZpZ operator/(ZpZ r) const { return ZpZ(value) /= r; }
  explicit operator long long int() const { return value; }
  explicit operator int() const { return value; }
  ZpZ operator-() { return P - value; }
  ZpZ inverse() {
    int a = value, b = P, u = 1, v = 0;
    while (b) {
      int t = a / b;
      std::swap(a -= t * b, b);
      std::swap(u -= t * v, v);
    }
    if (u < 0) u += P;
    return u;
  }
  ZpZ pow(U64 e) {
    U64 ret = 1, base = value;
    while (e) {
      if ((e & 1) && ((ret *= base) >> 32)) ret %= P;
      if ((base *= base) >> 32) base %= P;
      e >>= 1;
    }
    return ret;
  }
};
template <unsigned int P>
void WT(ZpZ<P> arg) {
  WT((int)arg);
}
struct Range {
  struct It {
    int num, step;
    int operator*() { return num; }
    void operator++() { num += step; }
    bool operator!=(const It& other) { return num != other.num; }
  };
  Range(int ee) : b(0), e(ee) {}
  Range(int bb, int ee) : b(bb), e(ee) {}
  It begin() { return {b, (b < e ? 1 : -1)}; }
  It end() { return {e, 0}; }
  int b, e;
};
template <typename T>
inline T& UMAX(T& x, T y) {
  if (x < y) x = y;
  return x;
}
template <typename T>
inline T& UMIN(T& x, T y) {
  if (y < x) x = y;
  return x;
}
template <typename T, typename... Args>
struct ArithmiticPromotion {
  typedef decltype(T() + typename ArithmiticPromotion<Args...>::type()) type;
};
template <typename T, typename U>
struct ArithmiticPromotion<T, U> {
  typedef decltype(T() + U()) type;
};
template <typename T>
struct ArithmiticPromotion<T, T> {};
template <typename T>
struct ArithmiticPromotion<T> {};
template <typename T, typename U>
typename ArithmiticPromotion<T, U>::T MAX(T a, U b) {
  return a < b ? b : a;
}
template <typename T, typename... Args>
typename ArithmiticPromotion<T, Args...>::T MAX(T a, Args... args) {
  return MAX(a, MAX(args...));
}
template <typename T, typename U>
typename ArithmiticPromotion<T, U>::T MIN(T a, U b) {
  return a < b ? a : b;
}
template <typename T, typename... Args>
typename ArithmiticPromotion<T, Args...>::T MIN(T a, Args... args) {
  return MIN(a, MIN(args...));
}
using RG = Range;
using namespace std;
const int MOD = 1e9 + 7;
using ZZ = ZpZ<MOD>;
char S[1000009];
int main() {
  RD(S);
  int N = strlen(S);
  ZZ ans = 0;
  ZZ b = 0;
  for (int i = N - 1; i >= 0; i--)
    if (S[i] == 'b')
      b += 1;
    else {
      ans += b;
      b *= 2;
    }
  WTL(ans);
}
