aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

inp = list(input())
lis = []
arr,brr = [0]*len(inp),[0]*len(inp)
ans=0
for i in range(len(inp)):
    if inp[i] == 'a':
        arr[i]=1
        ans+=1
    elif inp[i] == 'b':
        brr[i] = 1

i=0
while i<len(arr)-1:
    if arr[i] == 1:
        j=i+1
        while j<len(brr) and brr[j]!=1:
            j+=1
        if j<len(brr) and brr[j]==1:
            ans += sum(arr[:i+1]) * sum(arr[j:])
        i=j
    else:
        i+=1

ans = ans%1000000007
print(ans)