#include <bits/stdc++.h>
using namespace std;
inline long long int modadd(long long int n, long long int m,
                            long long int p = 1000000007) {
  return ((n + m) % p + p) % p;
}
inline long long int modsub(long long int n, long long int m,
                            long long int p = 1000000007) {
  return ((n - m + p) % p + p) % p;
}
inline long long int modpro(long long int n, long long int m,
                            long long int p = 1000000007) {
  return (((n % p) * (m % p)) % p + p) % p;
}
unsigned long long int powe(long long int first, long long int second) {
  unsigned long long int res = 1;
  while (second > 0) {
    if (second & 1) res = res * first;
    second = second >> 1;
    first = first * first;
  }
  return res;
}
long long int modpow(long long int first, long long int second,
                     long long int p = 1000000007) {
  long long int res = 1;
  while (second > 0) {
    if (second & 1) res = modpro(res, first, p);
    second = second >> 1;
    first = modpro(first, first, p);
  }
  return res;
}
inline long long int modInverse(long long int n, long long int p = 1000000007) {
  if (n == 1) return 1;
  return modpow(n, p - 2, p);
}
inline long long int moddiv(long long int n, long long int m,
                            long long int p = 1000000007) {
  return modpro(n, modInverse(m, p), p);
}
inline long long int modadd3(long long int first, long long int second,
                             long long int z, long long int p = 1000000007) {
  return modadd(modadd(first, second, p), z, p);
}
inline long long int modadd4(long long int first, long long int second,
                             long long int z, long long int w,
                             long long int p = 1000000007) {
  return modadd(modadd(first, second, p), modadd(z, w, p), p);
}
inline long long int modnCr(long long int fac[], int n, int r,
                            long long int p = 1000000007) {
  if (r == 0) return 1;
  return modpro(fac[n], modInverse(modpro(fac[r], fac[n - r], p), p), p);
}
template <typename T>
inline T max3(T first, T second, T z) {
  return max(max(first, second), z);
}
template <typename T>
inline T max4(T first, T second, T z, T w) {
  return max(max3(first, second, w), z);
}
template <typename T>
inline T min3(T first, T second, T z) {
  return min(min(first, second), z);
}
template <typename T>
inline T min4(T first, T second, T z, T w) {
  return min(min3(first, second, w), z);
}
template <typename T>
void printArr(T *arr, int s, int n) {
  for (int i = s; i <= n; i++) {
    cout << arr[i] << " ";
  }
  cout << endl;
}
vector<vector<int>> adj, adj1;
vector<int> dist;
vector<int> visited;
queue<int> q;
class Graph {
 public:
  int V;
  Graph(int V) {
    this->V = V;
    adj.resize(V);
    adj1.resize(V);
    visited.resize(V);
    dist.resize(V);
  }
  ~Graph() {
    adj.clear();
    visited.clear();
    dist.clear();
  }
  void addEdge(int a, int b) {
    adj[b].push_back(a);
    adj1[a].push_back(b);
  }
  void bfs(int first) {
    visited[first] = 1;
    q.push(first);
    dist[first] = 0;
    while (!q.empty()) {
      int s = q.front();
      q.pop();
      for (auto u : adj[s]) {
        if (visited[u]) continue;
        visited[u] = 1;
        dist[u] = dist[s] + 1;
        q.push(u);
      }
    }
  }
};
vector<pair<int, int>> v;
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  int erer = 1;
  for (int erer2 = (1); erer2 < (erer + 1); erer2++) {
    string s;
    cin >> s;
    int ca = 0, cb = 0;
    for (int i = (0); i < (((long long int)(s).size())); i++) {
      if (s[i] == 'a') {
        ca++;
        if (cb) {
          v.push_back({cb, 1});
          cb = 0;
        }
      }
      if (s[i] == 'b') {
        cb++;
        if (ca) {
          v.push_back({ca, 0});
          ca = 0;
        }
      }
    }
    if (cb) {
      v.push_back({cb, 1});
      cb = 0;
    }
    if (ca) {
      v.push_back({ca, 0});
      ca = 0;
    }
    long long int pro = 1;
    for (int i = (0); i < (((long long int)(v).size())); i++) {
      if (!v[i].second) {
        pro = modpro(pro, v[i].first + 1);
      }
    }
    cout << modsub(pro, 1);
  }
  return 0;
}
