#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N,K; cin >> N >> K;
    vector<int> P(N);
    for(auto &p : P) cin >> p,p--;
    vector<pair<int,int>> answer;
    for(int t=0; t<N; t++){
        for(int i=0; i+K<N; i++) if(P.at(i) > P.at(i+K)) answer.push_back({i,i+K}),swap(P.at(i),P.at(i+K));
    }
    for(int i=0; i<N; i++) if(P.at(i) != i){cout << "-1\n"; return 0;}
    cout << answer.size() << "\n";
    for(auto [a,b] : answer) cout << a+1 << " " << b+1 << "\n";
}