N, K = map(int, input().split())
P = list(map(int, input().split()))

ans = []
for _ in range(2000):
    for i in range(N-K):
        if P[i] > P[i+K]:
            ans.append((i, i+K))
            P[i], P[i+K] = P[i+K], P[i]

if all(P[i] <= P[i+1] for i in range(N-1)):
    print(len(ans))
    for l, r in ans:
        print(l+1, r+1)
else:
    print(-1)