#include<bits/stdc++.h>
#define CSP2026 using
#define RP namespace
#define PLUSPLUS std
CSP2026 RP PLUSPLUS;
#define debug(x) cout<<"clock="<<clock()<<' '<<#x<<'='<<(x)<<'\n'
//#define getchar getchar_unlocked
using ll=long long;
inline int rd(){int x=0,f=1;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-1;for(;isdigit(ch);ch=getchar())x=(x<<3)+(x<<1)+(ch^48);return x*f;}
inline ll rdll(){ll x=0;int f=1;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-1;for(;isdigit(ch);ch=getchar())x=(x<<3)+(x<<1)+(ch^48);return x*f;}
constexpr int N=1005;
int a[N],bcnt;
struct node{int x,y;}b[N*N];
signed main(){
	int n=rd(),k=rd();
	for(int i=1;i<=n;++i)a[i]=rd();
	for(int i=1;i<=k;++i){
		for(int j=n;j>=i;j-=k){
			for(int t=i;t+k<=j;t+=k){
				if(a[t]>a[t+k])swap(a[t],a[t+k]),b[++bcnt]={t,t+k};
				//cout<<i<<' '<<j<<' '<<t<<'\n';
				//for(int i=1;i<=n;++i)cout<<a[i]<<" \n"[i==n];
			}
		}
	}//for(int i=1;i<=n;++i)cout<<a[i]<<" \n"[i==n];
	if(!is_sorted(a+1,a+n+1))cout<<"-1\n";
	else{
		cout<<bcnt<<'\n';
		for(int i=1;i<=bcnt;++i)cout<<b[i].x<<' '<<b[i].y<<'\n';
	}
}