#include <bits/stdc++.h>
using namespace std;
int main() {
    int n,m,k; cin >> n >> m >> k;
    vector<pair<int,int>> a(m);
    for (int i = 0; i < m; i++) {
        cin >> a[i].first;
        a[i].second = i;
    }
    sort(a.begin(), a.end());
    vector<pair<int,int>> out;
    int i = 0, cnt = 1;
    while (i < m) {
        while (i < m && a[i].first < cnt) i++;
        for (int j = 0; j < k; j++) {
            if (i < m) {
                out.push_back({a[i].second+1,cnt});
                i++;
            }
        }
        cnt++;
    }
    cout << out.size() << '\n';
    for (int i = 0; i < out.size(); i++) cout << out[i].first << ' ' << out[i].second << '\n';
}