aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

s=input()
sss=''
for i in s:
    if i in ['a','b']:
        sss+=i 
from itertools import groupby
xxx=[''.join(g) for _, g in groupby(sss)]
xxx=[len(i)+1 for i in xxx if 'a' in i]
ans=1
if len(xxx)==1:
    print((xxx[0]-1)%1000000007)
else:
    for i in xxx:
        ans*=i 
    print((ans-1)%1000000007)


