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 GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
using namespace std;
template <class T>
T sqr(T x) {
  return x * x;
}
template <class T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
template <class T1, class T2>
T1 chmin(T1& x, const T2& y) {
  if (T1(y) < x) return x = y;
  return x;
}
template <class T1, class T2>
T1 chmax(T1& x, const T2& y) {
  if (T1(y) > x) return x = y;
  return x;
}
template <class T1, class T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  os << '{';
  bool was = false;
  for (const T& x : v) {
    if (was) os << ", ";
    was = true;
    os << x;
  }
  os << '}';
  return os;
}
template <class T>
ostream& operator<<(ostream& os, const set<T>& v) {
  os << '[';
  bool was = false;
  for (const T& x : v) {
    if (was) os << ", ";
    was = true;
    os << x;
  }
  os << ']';
  return os;
}
template <class T>
ostream& operator<<(ostream& os, const multiset<T>& v) {
  os << '[';
  bool was = false;
  for (const T& x : v) {
    if (was) os << ", ";
    was = true;
    os << x;
  }
  os << ']';
  return os;
}
template <class T1, class T2>
ostream& operator<<(ostream& os, const map<T1, T2>& m) {
  os << '<';
  bool was = false;
  for (const auto& x : m) {
    if (was) os << ", ";
    was = true;
    os << x;
  }
  os << '>';
  return os;
}
const int INF = (int)2e9;
const long long LINF = (long long)2e18;
const int MOD = (int)1e9 + 7;
const int MAXN = (int)1e6 + 10;
string s;
int ans = 0, lst = -1, cnt = 0;
int step[MAXN];
int main() {
  ios_base::sync_with_stdio(false);
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == 'b') lst = i;
  }
  step[0] = 1;
  for (int i = 1; i < MAXN; i++) step[i] = (step[i - 1] * 2) % MOD;
  if (lst == -1) {
    cout << 0;
    return 0;
  }
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == 'a') {
      cnt++;
      continue;
    }
    ans = (ans + step[cnt]) % MOD;
    ans = (ans - 1 + MOD) % MOD;
  }
  cout << ans;
}
