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

using namespace std;

struct rendeles {
    int sor,hat;
};

bool rule(rendeles x, rendeles y) {
    return x.hat<y.hat;
}
int main()
{
    int n,m,k; 
    cin>>n>>m>>k;
    vector<rendeles> a(m+1);
    
    //absolutely the same
    for(int i=1; i<=m; i++){
        cin>>a[i].hat; 
        a[i].sor=i;
    }
    //until here
    
    sort(a.begin()+1, a.end(), rule);
    //same just not vector sort
    
    vector<rendeles>b; 
    int lim=0, q=1;
    
    for(int i=1; i<=n; i++){
        lim=0;
        while(a[q].hat>=i && lim<k && q<=m){
            rendeles x; 
            x.hat=a[q].sor; 
            x.sor=i;
            b.push_back(x); 
            lim++; 
            q++;
        }
        while(a[q].hat==i) q++;
    }
        
    cout<<b.size()<<endl;
    for(rendeles x:b) cout<<x.hat<<" "<<x.sor<<endl;
    return 0;
}