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;
long long int bpow(long long int a, long long int b) {
  if (b == 0) return 1;
  long long int res = bpow(a, b / 2);
  if (b % 2)
    return res * res * a;
  else
    return res * res;
}
long long int bpowm(long long int x, long long int y, long long int m) {
  long long int res = 1;
  x = x % m;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x) % m;
    y = y >> 1;
    x = (x * x) % m;
  }
  return res;
}
long long int solve() {
  string s;
  cin >> s;
  vector<long long int> a;
  long long int n = s.size(), count = 0;
  for (long long int i = 0; i < n; i++) {
    if (s[i] == 'b') {
      if (count > 0) a.push_back(count);
      count = 0;
    } else if (s[i] == 'a') {
      count++;
    }
  }
  if (count > 0) a.push_back(count);
  long long int ans = 1;
  for (auto x : a) {
    ans *= (x + 1);
    ans %= 1000000007;
  }
  ans -= 1;
  ans %= 1000000007;
  cout << ans << "\n";
  return 0;
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int t;
  t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
