#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair< int , int > PII;

int n, a[100100], x, b[100100], pas[100100], mx;
string s;

multiset < pair < int , int > > M, W;
vector < int > V[100100];
bitset < 100100 > B;

void print (int x) {
    B[x] = 1;

    for (auto it : V[x]) {
        if (B[it]) continue;

        cout << x << " " << it << "\n";
        print (it);
    }
}

bitset < 100100 > viz;
void dfs(int x)
{
	viz[x] = 1;
	for (auto it : V[x])
		if (!viz[it]) pas[it] = pas[x] + 1, mx = max(pas[it], mx), dfs(it);
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin >> n >> x;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        M.insert({a[i], i});
    }

    int st = x / 2 + 1;
    int dr = st;

    b[1] = M.begin()->second;
    M.erase(M.begin());

    b[x + 1] = M.begin()->second;
    M.erase(M.begin());

    if (st == 1) {
        V[b[1]].push_back(b[2]);
        for (int i = 2; i <= x; i++) {
            V[b[i]].push_back(b[i - 1]);
            V[b[i]].push_back(b[i + 1]);
        }
        V[b[x + 1]].push_back(b[x]);

        print(1);
        return 0;
    }

    b[st] = M.rbegin()->second;

    int cp = M.rbegin()->first - 2;
    if (cp > 0) {
        W.insert({cp, M.rbegin()->second});
    }

    M.erase(*M.rbegin());

    if (x % 2 == 1) {
        ++dr;
        b[dr] = M.rbegin()->second;

        cp = M.rbegin()->first - 2;
        if (cp > 0) {
            W.insert({cp, M.rbegin()->second});
        }

        M.erase(*M.rbegin());
    }

    while (st > 2) {
        st--; dr++;
        b[st] = M.rbegin()->second;

        cp = M.rbegin()->first - 2;
        if (cp > 0) {
            W.insert({cp, M.rbegin()->second});
        }

        M.erase(*M.rbegin());

        b[dr] = M.rbegin()->second;
        cp = M.rbegin()->first - 2;
        if (cp > 0) {
            W.insert({cp, M.rbegin()->second});
        }

        M.erase(*M.rbegin());
    }

    V[b[1]].push_back(b[2]);
    for (int i = 2; i <= x; i++) {
        V[b[i]].push_back(b[i - 1]);
        V[b[i]].push_back(b[i + 1]);
    }
    V[b[x + 1]].push_back(b[x]);

    // for (auto it : W) {
    //     cout << it.first << " " << it.second << "\n";
    // }


    while (M.size()) {
        pair < int , int > node = *M.rbegin();
        pair < int , int > dad = *W.rbegin();

        M.erase(*M.rbegin());
        W.erase(*W.rbegin());

        V[dad.second].push_back(node.second);
        V[node.second].push_back(dad.second);

        if (node.first > 1) {
            W.insert({node.first - 1, node.second});
        }

        if (dad.first > 1) {
            W.insert({dad.first - 1, dad.second});
        }
    }

    // testing
    pas[1] = 0;
	int node;
	dfs(1);
	for (int i = 1; i <= n; i++)
		if (pas[i] == mx){node = i; break;}
	mx = 1;
	memset(pas, 0, sizeof(pas));
	viz.reset();
	pas[node] = 1;
	dfs(node);

    // cout << mx - 1 << "\n";
    // assert(W.size() == 0);

    // --------------------------------------

    print(1);
    // cout << W.size() << "\n";
	return 0;
}