aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
 public static void main(String[] args) throws Exception {
        //Scanner in = new Scanner(System.in);
        PrintWriter pw=new PrintWriter(System.out);
       BufferedReader br = new BufferedReader( 
                              new InputStreamReader(System.in)); 
        InputReader in=new InputReader(System.in);
        
        char[] str=in.nextLine().toCharArray();
        int n=str.length;

        int[] dp=new int[n];
        if(str[n-1]=='a')dp[n-1]=1;
        else dp[n-1]=0;

        for(int i=n-2;i>=0;i--){
            if(str[i]=='a')dp[i]=dp[i+1]+1;
            else dp[i]=dp[i+1];
        }
        long cnt=dp[0];
        
        int l=0;
        int r=0;
        while(l<n){
            if(str[l]=='a')break;
            l++;
        }
        
        r=l+1;
        int f=0;
        while(l<n && r<n){
            if(str[r]=='a'){
                if(f==1){
                    cnt+=dp[r];
                    //System.out.println(cnt);
                }
                l=r;
                f=0;
            }else if(str[r]=='b')f=1;
            r++;
        }

        cnt=cnt%(long)(1e9+7);
        pw.println(cnt);
        

        pw.flush();
        pw.close();
        
   }
   static class Pair implements Comparable<Pair>{
        int x;
        int y;
        Pair(int a,int b){
            x=a;
            y=b;
        }
        @Override
        public int compareTo(Pair t){
            if(x>t.x)return 1;
            else if(x==t.x){
                if(y>=t.y)return 1;
                else return -1;
            }
            else return -1;
        }
        @Override
        public boolean equals(Object obj){
            if(this==obj)return true;
            Pair that=(Pair)obj;
            if(this.x==that.x && this.y==that.y)return true;
            return false;
        }
    }
    static class InputReader {

        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        private SpaceCharFilter filter;

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

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

        public int nextInt() {
            int c = snext();
            while (isSpaceChar(c)) {
                c = snext();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = snext();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public long nextLong() {
            int c = snext();
            while (isSpaceChar(c)) {
                c = snext();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = snext();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public int[] nextIntArray(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }

        public long[] nextLongArray(int n) {
            long a[] = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextLong();
            }
            return a;
        }
                
        public String readString() {
            int c = snext();
            while (isSpaceChar(c)) {
                c = snext();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = snext();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public String nextLine() {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = snext();
            } while (!isEndOfLine(c));
            return res.toString();
        }

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

        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
}
