aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String args[]) throws Exception {
        Scan in = new Scan ();
        Print out = new Print ();

        String s = in.scanString();

        long sum = 0;

		int multiplier = 1;

        if(s.charAt(0) == 'a')
        	sum = 1;

        for(int i = 1; i < s.length(); i++) {
        	if(s.charAt(i) == 'a') {
        		sum += multiplier;
        	}
        	else if(s.charAt(i) == 'b') {
        		if(s.charAt(i - 1) == 'a')
        			multiplier++;
        	}
        	else {
        		multiplier = 1;
        	}
        }

        out.println(Long.valueOf(sum % 1000000007l).toString());

        out.close();
    }

    static class Scan {
		private byte[] buf=new byte[1024];
		private int index;
		private InputStream in;
		private int total;
		public Scan()
		{
			in=System.in;
		}
		public int scan()throws IOException
		{
			if(total<0)
			throw new InputMismatchException();
			if(index>=total)
			{
				index=0;
				total=in.read(buf);
				if(total<=0)
				return -1;
			}
			return buf[index++];
		}
		public int scanInt()throws IOException
		{
			int integer=0;
			int n=scan();
			while(isWhiteSpace(n))
			n=scan();
			int neg=1;
			if(n=='-')
			{
				neg=-1;
				n=scan();
			}
			while(!isWhiteSpace(n))
			{
				if(n>='0'&&n<='9')
				{
					integer*=10;
					integer+=n-'0';
					n=scan();
				}
				else throw new InputMismatchException();
			}
			return neg*integer;
		}
		public long scanLong()throws IOException
		{
			long integer=0;
			int n=scan();
			while(isWhiteSpace(n))
			n=scan();
			int neg=1;
			if(n=='-')
			{
				neg=-1;
				n=scan();
			}
			while(!isWhiteSpace(n))
			{
				if(n>='0'&&n<='9')
				{
					integer*=10;
					integer+=n-'0';
					n=scan();
				}
				else throw new InputMismatchException();
			}
			return neg*integer;
		}
		public double scanDouble()throws IOException
		{
			double doub=0;
			int n=scan();
			while(isWhiteSpace(n))
			n=scan();
			int neg=1;
			if(n=='-')
			{
				neg=-1;
				n=scan();
			}
			while(!isWhiteSpace(n)&&n!='.')
			{
				if(n>='0'&&n<='9')
				{
					doub*=10;
					doub+=n-'0';
					n=scan();
				}
				else throw new InputMismatchException();
			}
			if(n=='.')
			{
				n=scan();
				double temp=1;
				while(!isWhiteSpace(n))
				{
					if(n>='0'&&n<='9')
					{
						temp/=10;
						doub+=(n-'0')*temp;
						n=scan();
					}
					else throw new InputMismatchException();
				}
			}
			return doub*neg;
		}
		public String scanString()throws IOException
		{
			StringBuilder sb=new StringBuilder();
			int n=scan();
			while(isWhiteSpace(n))
			n=scan();
			while(!isWhiteSpace(n))
			{
				sb.append((char)n);
				n=scan();
			}
			return sb.toString();
		}
		private boolean isWhiteSpace(int n)
		{
			if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
			return true;
			return false;
		}
	}
 
	static class Print {
		private final BufferedWriter bw;
		public Print()
		{
			bw=new BufferedWriter(new OutputStreamWriter(System.out));
		}
		public void print(String str)throws IOException
		{
			bw.append(str);
		}
		public void println(String str)throws IOException
		{
			print(str);
			bw.append("\n");
		}
		public void flushedPrintln(String str)throws IOException {
			println(str);
			bw.flush();
		}
		public void close()throws IOException
		{
			bw.close();
		}
		public void flush() throws IOException {
			bw.flush();
		}
	} 
}
