aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author sumit
 */
public class Main {
      public static void main(String[] args) {
            InputStream inputStream = System.in;
            OutputStream outputStream = System.out;
            InputReader in = new InputReader(inputStream);
            OutputWriter out = new OutputWriter(outputStream);
            CTheFairNutAndString solver = new CTheFairNutAndString();
            solver.solve(1, in, out);
            out.close();
      }

      static class CTheFairNutAndString {
            public void solve(int testNumber, InputReader in, OutputWriter out) {
                  long mod = 1000000007;
                  String str = in.next();
                  StringBuilder s = new StringBuilder();
                  for (int i = 0; i < str.length(); i++) {
                        if (str.charAt(i) != 'a' && str.charAt(i) != 'b') {

                        } else {
                              s.append(str.charAt(i));
                        }
                  }
                  long ans = 1;
                  long temp = 1;
                  for (int i = 0; i < s.length(); i++) {
                        if (s.charAt(i) == 'a')
                              temp++;
                        else {
                              ans = ((ans % mod) * (temp % mod)) % mod;
                              temp = 1;
                        }
                  }
                  ans = ((ans % mod) * (temp % mod)) % mod;
                  out.printLine(ans - 1);
            }

      }

      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 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++];
            }

            public String next() {
                  int c = read();

                  while (isSpaceChar(c))
                        c = read();

                  StringBuilder res = new StringBuilder();

                  do {
                        res.appendCodePoint(c);

                        c = read();
                  } while (!isSpaceChar(c));

                  return res.toString();
            }

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

      }

      static class OutputWriter {
            private final PrintWriter writer;

            public OutputWriter(OutputStream outputStream) {
                  writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
            }

            public OutputWriter(Writer writer) {
                  this.writer = new PrintWriter(writer);
            }

            public void close() {
                  writer.close();
            }

            public void printLine(long i) {
                  writer.println(i);
            }

      }
}

