Ositus

import itertools
def ie(v, w, m, x, y):
    t=0
    for z in range(x):
        P=list(range(0, p-1))
        for j in range(y):
            S=list(range(v[m[z][j]][0], v[m[z][j]][1]))
            for k in S:
                if k in P:
                    P.remove(k)
        t+=2**len(P)
    return t
s=input()
p=len(s)
k=[]
l=[]
for i in range(p):
    if (s[i] in k):
        l.append([k.index(s[i]), i])
        k[k.index(s[i])]=False
    k.append(s[i])
n=len(l)
u=0
for i in range(1, n+1):
    m=list(itertools.combinations(list(range(0, n)), i))
    u+=(-1)**i*ie(l, p, m, len(m), i)
print((2**(p-1)+u)%(10**9+7))

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: TIME LIMIT EXCEEDED

Test 6

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 7

Group: 3

Verdict: TIME LIMIT EXCEEDED