aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;

public class Main {

    public static void main(String[] args) throws IOException {
        FastReader fr = new FastReader();
        FastWriter fw = new FastWriter();
        String s = fr.nextString();
        long dp = 0, ans = 0, mod = (long) (1e9 + 7);
        char lastChar = 'b';
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != 'a' && s.charAt(i) != 'b') continue;
            if (s.charAt(i) == 'a' && lastChar == 'b') {
                dp = dp + 1;
                ans += dp;
            } else if (s.charAt(i) == 'a') {
                ans += dp;
            } else if (s.charAt(i) == 'b') {
                dp = ans;
            }
            lastChar = s.charAt(i);
            ans %= mod;
        }
        fw.println(ans);
    }

}


class FastReader {
    public FastReader() {
    }

    public FastReader(String fileName) throws FileNotFoundException {
        this.br = new BufferedReader(new FileReader(fileName));
    }

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st;

    String nextString() throws IOException {
        if (st == null || !st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }

    int nextInt() throws IOException {
        return Integer.parseInt(nextString());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextString());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextString());
    }
}

class FastWriter {
    public FastWriter() {
    }

    public FastWriter(String fileName) throws IOException {
        this.bw = new BufferedWriter(new FileWriter(fileName));
    }

    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

    void print(Object o) throws IOException {
        bw.write(o.toString());
        bw.flush();
    }

    void println(Object o) throws IOException {
        print(o.toString() + "\n");
    }

    void printSp(Object o) throws IOException {
        print(o.toString() + " ");
    }
}