#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,s,n) for (int i = (s); i < (n); ++i)
#define rrep(i,g,n) for (int i = (n)-1; i >= (g); --i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define len(x) (int)(x).size()
#define dup(x,y) (((x)+(y)-1)/(y))
#define pb push_back
#define eb emplace_back
#define Field(T) vector<vector<T>>
using namespace std;
using ll = long long;
using ull = unsigned long long;
template<typename T> using pq = priority_queue<T,vector<T>,greater<T>>;
using P = pair<int,int>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}

int main() {
  int n, k;
  cin >> n >> k;
  vector<int> p(n);
  rep(i,0,n) cin >> p[i];
  vector<P> ans;
  rep(t,0,n) rep(i,0,n-k) {
    if (p[i] > p[i+k]) ans.eb(i, i+k), swap(p[i], p[i+k]);
  }
  rep(i,0,n) {
    if (p[i] != i+1) {
      cout << -1 << endl;
      return 0;
    }
  }
  cout << len(ans) << endl;
  for (auto [i, j] : ans) cout << i+1 << " " << j+1 << endl;
  return 0;
}