Pair sort

def pair_sort(m):
    n = len(m)

    positions = {}
    for idx, val in enumerate(m):
        if val not in positions:
            positions[val] = []
        positions[val].append(idx)

    swap_count = 0
    i = 0
    swaps = []
    used = [False] * n

    while i < n - 1:
        if used[i]:
            i += 1
            continue

        if m[i] == m[i + 1] and not used[i + 1]:
            used[i] = used[i + 1] = True
            i += 2
            continue

        target = m[i]

        for pos in positions[target]:
            if pos > i + 1 and not used[pos]:
                m[i + 1], m[pos] = m[pos], m[i + 1]
                swaps.append((i + 1, pos))
                swap_count += 1
                used[i] = used[i + 1] = True
                break
        i += 2

    return swap_count, swaps

n = int(input())
m = list(map(int,input().split()))
count, swaps = pair_sort(m, n)

print(count)
for swap in swaps:
    print(f"{swap[0]+1} {swap[1]+1}")



# print(*m)

Test 1

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 2

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 3

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 4

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 5

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 6

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 11

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 12

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 13

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...

Test 14

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 40, in <module>
    count,...