#include <iostream>
#include <vector>
using namespace std;
const int maxn = 1e3+10;
int a[maxn], n, s;

void fast_io() {

    ios_base :: sync_with_stdio(0);
    cin.tie(nullptr);
    cout.tie(nullptr);

}

void read() {

    cin >> n >> s;
    for (int i = 1 ; i <= n ; ++i)
        cin >> a[i];

}

vector < pair < int, int > > v;

void operation(int x, int y) {

    if (x < 1 || x > n || y < 1 || y > n) return;

    v.push_back({x, y});
    a[x] ^= a[y];

}

void solve() {

    int beg = 0;

    for (int log = 19 ; log >= 0 ; --log) {

        for (int i = 1 ; i <= n-beg ; ++i) {

            if (a[i] & (1 << log)) {

                if (i < n && (!(a[i+1] & (1 << log)))) operation(i+1, i);
                if (a[i-1] & (1 << log)) operation(i-1, i);

            }

        }

        beg += ((a[n-beg] & (1 << log)) > 0);

    }

    cout << v.size() << '\n';
    for (auto [x, y] : v)
        cout << x << ' ' << y << '\n';

}

void solve25() {

    int last_max = 0, max_ix;

    for (int iteration = 0 ; iteration < n-1 ; ++iteration) {

        max_ix = 1;
        for (int i = 2 ; i <= n-iteration ; ++i) {

            if ((a[i] ^ last_max) > (a[max_ix] ^ last_max)) max_ix = i;

        }

        for (int i = 1 ; i <= n-iteration - (iteration == 0) ; ++i) {

            operation(i, i+1);

        }

        for (int i = max_ix+1 ; i <= n-iteration ; ++i)
            operation(i, i-1);

        for (int i = max_ix-2 ; i >= 1 ; --i)
            operation(i, i+1);

        last_max = a[n-iteration];

    }

    operation(1, 2);

    // cout << "a: ";
    // for (int i = 1 ; i <= n ; ++i)
    //     cout << a[i] << ' ';
    // cout << '\n';

    // return;

    cout << v.size() << '\n';
    for (auto [x, y] : v)
        cout << x << ' ' << y << '\n';

}

signed main () {

    fast_io();
    read();
    if (s == 1) solve25();
    else solve();

    return 0;

}