#ifndef ONLINE_JUDGE
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll=long long;
using ld=long double;
using st=string;
using P=pair<ll,ll>;
typedef atcoder::modint mint;
ll inf=9e18;
template<class... T>
constexpr auto max(T... a){return max(initializer_list<common_type_t<T...>>{a...});}
template<class... T>
constexpr auto min(T... a){return min(initializer_list<common_type_t<T...>>{a...});}
template<typename T, int s, int i = 0>
auto vec(const ll (&sizes)[s], const T& init = T()){
  if constexpr(i < s) return vector(sizes[i], vec<T, s, i+1>(sizes, init));
  else return init;
}


int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  
  ll n,k;
  cin>>n>>k;
  auto v=vec<ll>({n},0);
  auto ans=vec<ll>({0},0);
  for(ll i=0;i<n;i++){
    cin>>v[i];
  }
  for(ll i=0;i<n;i++){
    for(ll j=0;j<n-k;j++){
      if(v[j]>v[j+k]){
        ans.push_back(j);
        swap(v[j],v[j+k]);
      }
    }
  }
  for(ll i=0;i<n;i++){
    if(v[i]!=i+1) {cout<<-1<<"\n";return 0;}
  }
  cout<<ans.size()<<"\n";
  for(ll i=0;i<ans.size();i++){
    cout<<ans[i]+1<<" "<<ans[i]+k+1<<"\n";
  }
}