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>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
const int INF = 1000001000;
const long long INFLL = INF * 1LL * INF;
const int mod = 1000 * 1000 * 1000 + 7;
const int mod9 = 1000 * 1000 * 1000 + 9;
const int modr = 99990001;
const long double PI = 3.1415926535897932385;
template <class T>
void zero(T val, T& first) {
  first = val;
}
template <class T, class... Targs>
void zero(T val, T& first, Targs&... Fargs) {
  first = val;
  zero(val, Fargs...);
}
template <class T, class T2>
std::istream& operator>>(std::istream& is, pair<T, T2>& p) {
  return is >> p.first >> p.second;
}
template <class T>
std::istream& readN(T& first, int n, int st = 0) {
  for (int i = st, iend = (st + n - 1); i <= iend; i++) cin >> first[i];
  return cin;
}
template <class T>
std::istream& readS(set<T>& first, int n) {
  T second = *first.rbegin();
  for (int i = 0, iend = (n - 1); i <= iend; i++) {
    cin >> second;
    first.insert(second);
  }
  return cin;
}
template <class T>
std::istream& read(T& first) {
  return cin >> first;
}
template <class T, class... Targs>
std::istream& read(T& first, Targs&... Fargs) {
  return read(first), read(Fargs...);
}
template <class T, class T2>
std::ostream& operator<<(std::ostream& os, pair<T, T2> p) {
  return os << p.first << " " << p.second;
}
template <class T>
std::ostream& operator<<(std::ostream& os, vector<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& operator<<(std::ostream& os, set<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& operator<<(std::ostream& os, multiset<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T, class T2>
std::ostream& operator<<(std::ostream& os, map<T, T2> v) {
  bool f = true;
  for (pair<T, T2> second : v) {
    if (!f) os << ' ';
    os << second.first << "=>" << second.second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& outV(T first, char del = ' ') {
  bool f = true;
  for (auto second : first) {
    if (!f) cout << del;
    cout << second;
    f = false;
  }
  return cout;
}
template <class T>
std::ostream& outN(T first, int n = -1, int st = 0) {
  for (int i = st, iend = (n == -1 ? (int)first.size() - 1 : st + n - 1);
       i <= iend; i++) {
    cout << first[i];
    if (i < iend) cout << ' ';
  }
  return cout;
}
template <class T>
std::ostream& outAN(T first, int n = -1, int st = 0) {
  for (int i = st, iend = (n - 1); i <= iend; i++) {
    cout << first[i];
    if (i < iend) cout << ' ';
  }
  return cout;
}
template <class T>
std::ostream& outA2(T first, int n, int m) {
  for (int i = 0, iend = (n - 1); i <= iend; i++) {
    for (int j = 0, jend = (m - 1); j <= jend; j++)
      cout << first[i][j] << (j == m - 1 ? '\n' : ' ');
  }
  return cout;
}
template <class T>
std::ostream& out(T first) {
  return cout << first;
}
template <class T, class... Targs>
std::ostream& out(T first, Targs... Fargs) {
  return out(first) << " ", out(Fargs...);
}
template <typename T>
void srt(T& a, int st, int fn, bool isArr) {
  sort(a + st, a + fn + 1);
}
template <class T>
void srt(T& a, int st = 0, int fn = 0) {
  sort(a.begin() + st, fn ? a.begin() + fn + 1 : a.end());
}
template <typename T>
T rev_num(T a) {
  T r = 0;
  for (; a; a /= 10) r = r * 10 + a % 10;
  return r;
}
template <typename T>
void rev(T& a, int st, int fn, bool isArr) {
  reverse(a + st, a + fn + 1);
}
template <class T>
void rev(T& a, int st = 0, int fn = 0) {
  reverse(a.begin() + st, fn ? a.begin() + fn + 1 : a.end());
}
long long sqr(long long a) { return a * a; };
long long sqr(int a) { return a * 1LL * a; };
long double sqr(long double a) { return a * a; };
long double dist(pair<long long, long long> first,
                 pair<long long, long long> second) {
  return sqrt(sqr(first.first - second.first) +
              sqr(first.second - second.second));
}
long long phi(int n) {
  int res = n;
  for (long long i = 2; i * i <= n; i++)
    if (n % i == 0) {
      while (n % i == 0) n /= i;
      res -= res / i;
    }
  if (n > 1) res -= res / n;
  return res;
}
long long bpm(long long a, long long n = -2, long long m = mod) {
  n = n < 0 ? n + m : n;
  long long r = 1;
  while (n) {
    if (n & 1) r = (r * a) % m;
    a = (a * a) % m;
    n >>= 1;
  }
  return r;
}
unsigned long long gcd(unsigned long long a, unsigned long long b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
vector<int> ero_p, ero_l;
void ero(int n) {
  ero_l.resize(n + 1);
  ero_l[0] = -1;
  for (int i = 2, iend = (n); i <= iend; i++)
    if (!ero_l[i]) {
      ero_p.push_back(i);
      ero_l[i] = i;
      for (long long j = i * 1LL * i; j <= n; j += i) {
        ero_l[j] = i;
      }
    }
}
long long gcd_cb(long long a, long long b, long long& first,
                 long long& second) {
  if (!b) {
    first = 1;
    second = 0;
    return a;
  }
  long long x1, y1, g;
  g = gcd_cb(b, a % b, x1, y1);
  first = y1;
  second = x1 - a / b * y1;
  return g;
}
vector<long long> fact;
void fact_prec(int n = 20) {
  fact.resize(n + 1);
  fact[0] = 1;
  for (int i = 1, iend = (n); i <= iend; i++) {
    fact[i] = fact[i - 1] * i;
  }
}
vector<long double> factd;
void fact_precd(int n = 146) {
  factd.resize(n + 1);
  factd[0] = 1;
  for (int i = 1, iend = (n); i <= iend; i++) {
    factd[i] = factd[i - 1] * i;
  }
}
string str(long long a) {
  string r = "";
  for (; a; a /= 10) r += a % 10 + '0';
  rev(r);
  return r;
}
template <class T>
int bitc(T first) {
  int r = 0;
  for (T d = first; d >= 0; d >>= 1) r += d & 1;
  return r;
}
const int N = 200005;
int main() {
  string s;
  read(s);
  long long st = 0, c = 0;
  for (int i = s.length() - 1; i >= 0; i--) {
    if (s[i] == 'b') {
      c++;
    } else {
      st += c;
      c *= 2;
      c %= mod;
      st %= mod;
    }
  }
  out(st) << "\n";
  return 0;
}
