#include <bits/stdc++.h>
#define mp make_pair
#define F first
#define S second
#define eb emplace_back
#define printv(a, b) { \
for(auto pv : a) b << pv << " "; \
b << "\n"; \
}
using namespace std;
typedef long long ll;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
const ll MAX = 1LL << 60;
ostream& operator<<(ostream& o, pll p){
return o << '(' << p.F << ',' << p.S << ')';
}
ll iceil(ll a, ll b){
return (a + b - 1) / b;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
ll n, k;
cin >> n >> k;
ll a = 0;
for(int i = 1; i <= n; i++){
ll t;
cin >> t;
if(i != 1) assert(a == t);
a = t;
}
ll g = __gcd(n, k);
if(a * n % k || n * k / g > 3000000){
cout << "-1\n";
return 0;
}
ll t = k / g;
ll v = a / t;
cout << n / g << "\n";
int now = 0;
for(int i = 0; i < n / g; i++){
cout << v << " ";
for(int j = 0; j < k; j++){
cout << 1 + now % n << " ";
now++;
}
cout << "\n";
}
return 0;
}
