#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <vector>
#include <stack>
using namespace std;
#define int long long
#define mp make_pair
#define fi first
#define pii pair<int,int>
#define se second
const int INF=1000000000000000000;
//const int INF=1e9;
const int N=1000000;
const int M=998244353;
const int ln=20;
template<typename T>
std::ostream& operator<< (std::ostream& os,pair<T,T> p){
return os << p.fi << "," << p.se << " ";
}
void solve(){
int n,k;
cin >> n >> k;
int g=1;
for(int i=1;i<=n;i++){
if(n%i==0 && k%i==0) g=i;
}
int a[n];
for(int i=0;i<n;i++){
cin >> a[i];
assert(a[i]==a[0]);
}
if(a[0]%(k/g)!=0){
cout << -1 << "\n";
return;
}
int x=a[0]/(k/g);
cout << n/g << "\n";
for(int i=0;i<n/g;i++){
cout << x << " ";
for(int j=0;j<k;j++){
cout << (i*(g)+j)%n+1LL << " ";
}
cout << "\n";
}
}
signed main(){
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int t;
//cin >> t;
t=1;
while(t--) solve();
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
}
