Problem: Snuke has an integer sequence, a, of length N. The i-th element of a (1-indexed) is a_{i}.

He can perform the following operation any number of times:

* Operation: Choose integers x and y between 1 and N (inclusive), and add a_x to a_y.



He would like to perform this operation between 0 and 2N times (inclusive) so that a satisfies the condition below. Show one such sequence of operations. It can be proved that such a sequence of operations always exists under the constraints in this problem.

* Condition: a_1 \leq a_2 \leq ... \leq a_{N}

Constraints

* 2 \leq N \leq 50
* -10^{6} \leq a_i \leq 10^{6}
* All input values are integers.

Input

Input is given from Standard Input in the following format:


N
a_1 a_2 ... a_{N}


Output

Let m be the number of operations in your solution. In the first line, print m. In the i-th of the subsequent m lines, print the numbers x and y chosen in the i-th operation, with a space in between. The output will be considered correct if m is between 0 and 2N (inclusive) and a satisfies the condition after the m operations.

Examples

Input

3
-2 5 -1


Output

2
2 3
3 3


Input

2
-1 -3


Output

1
2 1


Input

5
0 0 0 0 0


Output

0

Solution (in CPP):

Solution:
#include <bits/stdc++.h>

#define rep(i, n) for(int i = 0; i<(n); i++)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
typedef long long ll;

typedef pair<int, int> P;

int main() {
    int N;
    cin >> N;
    vector<int> a(N);
    rep(i, N) cin >> a[i];

    int m_i = 0;
    rep(i, N) {
        if (abs(a[m_i]) < abs(a[i])) m_i = i;
    }

    vector<P> ans;
    rep(i, N) {
        if (m_i == i) continue;
        ans.push_back(make_pair(m_i + 1, i + 1));
    }

    if (a[m_i] > 0) {
        rep(i, N - 1) ans.push_back(make_pair(i + 1, i + 2));
    } else {
        for (int i = N - 1; i > 0; i--) ans.push_back(make_pair(i + 1, i));
    }

    cout << ans.size() << endl;
    rep(i, ans.size()) cout << ans[i].first << " " << ans[i].second << endl;
}