list1 = [1, 5, 4, 8, 9, 11, 3]
while True:
    try:
        k = int(input("基準値を入力してください: "))
        break
    except ValueError:
        print("エラー")

success = 0

for i in range(len(list1)):
    for j in range(i+1, len(list1)):
        if i != j:
            if (list1[i]+list1[j]) % k == 0:
                success += 1
print(f"合計が{k}の倍数になるペアは{success}通りです")