// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;
#define int long long
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n,m,k;cin>>m>>n>>k;
    vector<pair<int,int>> v(n);
    for(int i = 0;i<n;i++){
        cin>>v[i].first;
        v[i].second=i+1;
    }
    sort(v.begin(),v.end());
    vector<pair<int,int>> ans;
    int j = 0;
    for(int i = 1;i<=m;i++){
        int cnt=0;
        while(j<n&&v[j].first<i)j++;
        while(cnt<k&&j<n&&i<=v[j].first){
            ans.push_back({v[j].second,i});
            j++;
            cnt++;
        }
    }
    cout<<ans.size()<<endl;
    for(auto [a,b]:ans){
        cout<<a<<' '<<b<<endl;
    }
}