aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;

public class C {

    private static final long Modulo = 1000_000_007;

    private static int pos, len;
    private static long max, min, cur, ans, res, sum, preB;
    private static int ai, bi, ci, di;
    private static int[] aix, bix;
    private static int[][] aixx, bixx;
    private static long al, bl, cl, dl;
    private static long[] alx, blx;
    private static long[][] alxx, blxx;
    private static double ad, bd, cd, dd;
    private static double[] adx, bdx;
    private static double[][] adxx, bdxx;
    private static boolean ab, bb, cb, db;
    private static boolean[] abx, bbx;
    private static boolean[][] abxx, bbxx;
    private static char ac, bc, cc, dc;
    private static char[] acx, bcx;
    private static char[][] acxx, bcxx;
    private static String as, bs, cs, ds;
    private static InputReader in = new InputReader(System.in);
    private static PrintWriter out = new PrintWriter(System.out);

    public static void main(String[] args) {
        as = in.next();
        acx = as.toCharArray();
        len = acx.length;
        alx = new long[len];

        alx[0] = acx[0] == 'a' ? 1L : 0L;
        preB = 0;
        for (int i = 1; i < len; i++) {
            if (acx[i] == 'a') {
                alx[i] = (alx[i - 1] + preB + 1) % Modulo;
            } else if (acx[i] == 'b') {/**/
                preB = alx[i - 1];
                alx[i] = alx[i - 1];
            } else {
                alx[i] = alx[i - 1];
            }
        }
        out.println(alx[len-1]);
        out.close();
    }

    private static class InputReader {

        private InputStream stream;

        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public String next() {
            return readString();
        }

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

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

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

        private boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        private int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }
    }
}