Ositus

I="aybebtuecdaceu"#+"ghsdfgljkaseifsdccfgsfbdvkfsdffdgfbdruffvrvfnvfsfdgefaslnghfo"
#555929291
I=input()
ends=[1]
minimum=0
rising=False
for i in range(1,len(I)):
    if rising:
        t=ends[-1]*2
    else:
        t=sum(ends)%(7+(10**9))
    s=I[i]
    cut=I.rfind(s,minimum,i)
    if minimum<cut+1:
        oldmin=minimum
        minimum=cut+1
        ends = ends[minimum-oldmin:]
        rising=False
    else:
        rising=True
    ends.append(t)
    # print("{} {} {}".format(ends,rising, t*2))
total = sum(ends)
print(total%(7+(10**9)))

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: ACCEPTED

Test 6

Group: 3

Verdict: ACCEPTED

Test 7

Group: 3

Verdict: ACCEPTED