#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
struct rendeles
{
    int hnap,ssz;
};
struct rendeles2
{
    int rssz,nap;
};
vector <rendeles> a;
vector <rendeles2> eredm;

bool hasonlit(rendeles x,rendeles y){
        return x.hnap<y.hnap;
}
int main()
{
    int n,m,k;
    rendeles x;
    cin>>n>>m>>k;
    for(int i=1;i<=m;i++)
    {
        cin>>x.hnap;
        x.ssz=i;
        a.push_back(x);
    }
    sort(a.begin(),a.end(),hasonlit);
    ///for(int i=0;i<m;i++) cout<<a[i].hnap<<" "<<a[i].ssz<<endl;
    int j=0,h=0;
    rendeles2 xx;
    for(int i=1;i<=n;i++)
    {
        int db=0;
        while(j<m && a[j].hnap>=i && db<k)
        {
            xx.rssz=a[j].ssz;
            xx.nap=i;
            eredm.push_back(xx); h++;
            j++;
            db++;
        }
        while(a[j].hnap<=i) j++;
    }
    cout<<h<<endl;
    for(int i=0;i<h;i++) cout<<eredm[i].rssz<<" "<<eredm[i].nap<<endl;
    return 0;
}