aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.*;
import java.util.*;

/**
 * +1 mmr plz? :3
 */
public class Main {

    static class Task {
        PrintWriter out;
        MyScanner in;

        long mod = 1_000_000_000 + 7;

        public void solve(MyScanner in, PrintWriter out) {
            this.out = out;
            this.in = in;

            List<Integer> nums = new ArrayList<>();

            String s = in.nextLine();
            int last = 0;
            for (int i = 0; i < s.length(); i++) {
                char c = s.charAt(i);
                if ('a' == c) {
                    last++;
                }
                if ('b' == c && last > 0) {
                    nums.add(last);
                    last = 0;
                }
            }

            if (last > 0) {
                nums.add(last);
            }

            /*for (int i = 0; i < nums.size(); i++) {
                System.out.print(" " + nums.get(i));
            }
            System.out.println();*/

            long[] a = new long[nums.size()];

            for (int i = 0; i < nums.size(); i++) {
                a[i] = nums.get(i);
            }

            if (nums.size() == 0) {
                System.out.println("0");
                return;
            }

            long[][] F = new long[nums.size()][2];
            F[0][0] = 0;
            F[0][1] = a[0];

            int n = nums.size();

            for (int i = 1; i < n; i++) {
                F[i][0] = mod(F[i - 1][0] + F[i-1][1]);
                F[i][1] = mod(a[i] + a[i] * (F[i - 1][0] + F[i-1][1]));
            }

            long ans = mod(F[n - 1][0] + F[n-1][1]);
            System.out.println(ans);
        }

        long mod(long s) {
            return s % mod;
        }

    }

    public static void main(String[] args) {
        MyScanner in = new MyScanner();
        PrintWriter out = new PrintWriter(System.out);
        Task solver = new Task();
        solver.solve(in, out);
        out.close();
    }

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}