#include <bits/stdc++.h>

using namespace std;

#define fst ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);

const int N = 1e5 + 10, inf = 0x3f3f3f3f;

int n, a[N], cnt, b[N], nxt[N];

struct node { int mx, id; } tr[N << 2];

#define lson (rt << 1)
#define rson (rt << 1 | 1)
#define mid (l + r) / 2

void push_up(node &a, node b, node c)
{
    if (b.mx > c.mx) a = b;
    else a = c;
}

void build(int rt, int l, int r, int a[])
{
    if (l == r) return tr[rt] = { a[l], l }, void();
    build(lson, l, mid, a);
    build(rson, mid + 1, r, a);
    push_up(tr[rt], tr[lson], tr[rson]);
}

void update(int rt, int l, int r, int p, int v)
{
    if (l == r) return tr[rt].mx += v, void();
    if (p <= mid) update(lson, l, mid, p, v);
    else update(rson, mid + 1, r, p, v);
    push_up(tr[rt], tr[lson], tr[rson]);
}

node query(int rt, int l, int r, int sp, int ep)
{
    if (sp <= l && r <= ep) return tr[rt];
    node res; bool f = 0;
    if (sp <= mid) res = query(lson, l, mid, sp, ep), f = 1;
    if (ep > mid) {
        if (f) push_up(res, res, query(rson, mid + 1, r, sp, ep));
        res = query(rson, mid + 1, r, sp, ep);
    }
    return res;
}

multiset<pair<int, int>> q;

int main()
{
    fst
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    build(1, 1, n, a);
    int res = 0, cnt = 0;
    while (1) {
        auto t = tr[1];
        if (!t.mx) break;
        update(1, 1, n, t.id, -t.mx);
        auto k = tr[1];
        int c = 0;
        if (!k.mx) { // 只剩我自己了
            cnt = t.mx;
            c = t.mx;
            for (int i = 1; i <= c; i++) q.insert({t.id, t.id});
        } else {
            c = min(t.mx, k.mx);
            update(1, 1, n, k.id, -c);
            res += c;
            for (int i = 1; i <= c; i++) q.insert({min(t.id, k.id), max(t.id, k.id)});
        }
        update(1, 1, n, t.id, t.mx - c);
    }
    cout << res + cnt << "\n";
    for (auto u : q) cout << u.first << " " << u.second << "\n";
    return 0;
}