#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
    int n,m,k; cin>>n>>m>>k;
    vector<pair<int,int>> x(m+1);
    for (int i=1;i<=m;++i) {
        cin>>x[i].first;
        x[i].second=i;
    }
    sort(x.begin(),x.end());
    int t=1, i=1, f=1, db=0;
    vector<pair<int,int>> meg;
    while (t<=n){
        if (i>m) break;
        else if (f<=k && x[i].first>=t){
            ++db;
            ++f;
            meg.push_back({x[i].second, t});
            ++i;
        }
        else if (x[i].first<t) ++i;
        else if (f>k){
            ++t;
            f=1;
        }
    }
    cout<<db<<"\n";
    for (int i=0;i<meg.size(); ++i){
        cout<<meg[i].first<<" "<<meg[i].second<<"\n";
    }
}