#include "bits/stdc++.h"
using namespace std;
#define ar array
const int mod = 2020;
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
int n, k; cin>>n>>k;
vector<int> a(n);
for(int i=0;i<n;i++) cin>>a[i];
vector<int> b(k);
for(int i=0;i<n;i++){
b[i%k] = (b[i%k] + a[i]) % k;
}
for(int i=1;i<n%k;i++){
if(b[i] != b[i-1]) {
cout<<-1<<"\n";
return 0;
}
}
for(int i=n%k+1;i<k;i++){
if(b[i] != b[i-1]){
cout<<-1<<"\n";
return 0;
}
}
vector<ar<int, 2>> res;
for(int i=1;i<n;i++){
while(a[i] < a[i-1]){
res.push_back({i, 0});
a[i] += k;
}
}
int tmp = (a[n-1] + k - 1) / k * k;
vector<int> cnt(tmp + 1, n);
for(int r=1;r<=tmp;r++){
for(int i=n-1;~i;i--){
if(a[i] >= r) cnt[r]--;
else if(i >= k - 1){
i = i-k+1;
res.push_back({i, 1});
cnt[r]-=k;
}
}
}
vector<int> d(k);
for(int i=0;i<k-1;i++){
int tot = 0;
for(int j=k;j<=tmp;j+=k){
res.push_back({i, 0});
for(int r=j-k+1;r<=j;r++){
if(!cnt[r]) continue;
if(cnt[r] == 1) tot++;
cnt[r]--;
}
}
d[i] = tot;
}
for(int i=k-2;~i;i--){
if(i+2 < k) d[i] += d[i+1];
a[i] = tmp - d[i];
while(a[i] < tmp) res.push_back({i, 0}), a[i] += k;
}
for(int i=n-1;i>=k-1;i--){
for(int l=0;l<tmp/k;l++){
res.push_back({i, 0});
}
}
if(n%k){
a[0] -= tmp;
for(int r=0;r<a[0];r++){
for(int i=n%k;i<n;i+=k){
res.push_back({i, 1});
}
}
}
cout<<(int)res.size()<<"\n";
for(auto x : res){
cout<<x[1] + 1<<" "<<x[0] + 1<<"\n";
}
}
