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

ans = []
while(True):
    flag = False
    for i in range(N-K):
        if(P[i] > P[i+K]):
            ans.append((i+1,i+K+1))
            P[i],P[i+K] = P[i+K],P[i]
            flag = True
    if(not flag):break

if(P == sorted(P)):
    print(len(ans))
    for i in ans:
        print(*i)
else:
    print(-1)