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:32000000")
const int nil = -1;
using namespace std;
inline bool read(int& val) { return scanf("%d", &val) != -1; }
inline bool read(long long& val) { return scanf("%I64d", &val) != -1; }
inline bool read(double& val) { return scanf("%lf", &val) != -1; }
inline bool read(char* val) { return scanf("%s", val) != -1; }
template <class T1, class T2>
inline bool read(T1& a, T2& b) {
  return read(a) && read(b);
}
template <class T1, class T2, class T3>
inline bool read(T1& a, T2& b, T3& c) {
  return read(a) && read(b) && read(c);
}
template <class T1, class T2, class T3, class T4>
inline bool read(T1& a, T2& b, T3& c, T4& d) {
  return read(a) && read(b) && read(c) && read(d);
}
template <class T1, class T2, class T3, class T4, class T5>
inline bool read(T1& a, T2& b, T3& c, T4& d, T5& e) {
  return read(a) && read(b) && read(c) && read(d) && read(e);
}
const int N = 1111111;
const long long mod = 1000000007;
char str[N];
long long cnt[N];
int main() {
  read(str);
  int n = strlen(str);
  cnt[0] = 0;
  long long sum = 0;
  long long pow2 = 1;
  for (int i = 0, _ = (n); i < _; ++i) {
    if (str[i] == 'a') {
      pow2 = pow2 * 2 % mod;
    } else {
      sum = (sum + pow2 - 1) % mod;
    }
  }
  cout << sum % mod << endl;
  return 0;
}
