Osajono

import math
import cProfile

def binomialCoefficient(n, k):
    if n < k:
        return 0
    return math.factorial(n) / (math.factorial(k) * (math.factorial(n - k)))


input = input()

if len(input) == 0:
    print (0)
    sys.exit()

letterCounts = [0] * 26

for i in range(0, len(input)):
    letter = ord(input[i])
    letterCounts[letter - 65] += 1

subsets = 0
for i in range(0, 26):
    subsets += (binomialCoefficient(letterCounts[i], 2) + letterCounts[i])
    
print (math.floor(subsets))
 

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED