aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class A {
    static MyScanner sc;
    static PrintWriter pw;

    public static void main(String[] args) throws Throwable {
        sc = new MyScanner();
        pw = new PrintWriter(System.out);

        int mod = (int) 1e9 + 7;
        char[] s = sc.next().toCharArray();
        int n = s.length;
        int[] lstB = new int[n];
        lstB[0] = -1;
        for (int i = 1; i < n; i++)
            lstB[i] = (s[i - 1] == 'b' ? i - 1 : lstB[i - 1]);
        long[] sum = new long[n];
        for (int i = 0; i < n; i++) {
            long tmp = 0;
            if (s[i] == 'a') {
                tmp++;
                if (lstB[i] != -1)
                    tmp += sum[lstB[i]];
            }
            sum[i] = tmp + (i > 0 ? sum[i - 1] : 0);
            sum[i] %= mod;
        }
        pw.println(sum[n - 1]);
        pw.flush();
        pw.close();
    }

    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;
        }
    }
}