Repeating substring

string = input()

if len(set(string)) == 1:
    print(string)
else:
    n = len(string)
    for le in range(n-1, 0, -1):
        i, j = 0, le
        while j < n:
            if string[i] != string[j]:
                break
            i += 1
            i %= le
            j += 1
        else:
            print(string[:le])
            break

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: ACCEPTED

Test 15

Verdict: WRONG ANSWER