aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

#include <bits/stdc++.h>
using namespace std;
template <typename T>
void clear(T& t) {
  t.clear();
}
template <typename T, typename... Ts>
void clear(T& t, Ts&... ts) {
  t.clear();
  clear(ts...);
}
template <typename T>
void clearAndResize(int n, T& t) {
  t.clear();
  t.resize(n);
}
template <typename T, typename... Ts>
void clearAndResize(int n, T& t, Ts&... ts) {
  t.clear();
  t.resize(n);
  clearAndResize(n, ts...);
}
template <class T>
ostream& operator<<(ostream& o, const vector<T>& v) {
  for (auto a : v) o << a << " ";
  return o;
}
template <class T, class U>
ostream& operator<<(ostream& o, const pair<T, U>& p) {
  o << "(" << p.first << ", " << p.second << ") ";
  return o;
}
const long long mod = 1e9 + 7;
int32_t main(int argv, char** argc) {
  ios::sync_with_stdio(false);
  string str;
  cin >> str;
  vector<long long> dp(str.size());
  int prevA = 0, prevB = 0;
  for (int i = 1; i <= str.size(); i++) {
    if (str[i - 1] == 'a') {
      if (prevA == 0) {
        dp[i] = dp[prevB] * 2 + 1;
      } else
        dp[i] = dp[prevA] + dp[prevB] + 1;
      dp[i] %= mod;
      prevA = i;
    }
    if (str[i - 1] == 'b') {
      if (prevA != 0) prevB = prevA;
      prevA = 0;
    }
  }
  if (prevA == 0)
    cout << dp[prevB] << endl;
  else
    cout << dp[prevA] << endl;
}
