#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector <ll>;
using ii = pair <ll, ll>;
using vii = vector <ii>;
const ll MAXN = 1E3+16;
ll th[MAXN];
vii ans;
vll ve;
void fop (ll i, ll j) {
ans.push_back({ i, j });
ve[i] ^= ve[j];
}
int main () {
cin.tie(nullptr) -> sync_with_stdio(false);
ll n, s;
cin >> n >> s;
ve = vll(n);
for (ll &i : ve) cin >> i;
ll nend = n;
for (ll bit = 19; bit >= 0; bit--) {
vll th = ve;
for (ll &i : th) i = i>>bit&1;
ll j = find(th.begin(), th.begin()+nend, 1) - th.begin();
for (ll i = j+1; i < nend; i++) {
if (th[i]) continue;
fop(i, i-1);
}
for (ll i = j+1; i < nend; i++) {
fop(i-1, i);
}
if (j != nend) nend--;
}
return 0;
}
