/////////////////////include/////////////////////
//#include <bits/stdc++.h>
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <cassert>
#include <set>
#include <map>
#include <unordered_map>
#include <vector>
#include <stack>
#include <queue>
#include <iomanip>
#include <bitset>
#include <stdio.h>
#include <climits>
#include <numeric>
using namespace std;
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//template <typename T>
//using ordered_set = tree <T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
/////////////////////define/////////////////////
#define ci(x) if(x) cout << "YES" << '\n'; else cout << "NO" << '\n';
#define cii(x) if(check(x))
#define MOD 1000000007
#define MOD2 998244353
#define oo 1e9
#define ool 1e18L
#define pii pair<int, int>
#define pll pair<long long, long long>
#define mii map<int, int>
#define vi vector<int>
#define vpi vector<pair<int, int>>
#define vll vector <ll>
#define ff first
#define ss second
#define mp make_pair
#define ll long long
#define ld long double
#define pb push_back
#define eb emplace_back
#define pob pop_back
#define lb lower_bound
#define ub upper_bound
#define bs binary_search
#define sz(x) (int((x).size()))
#define all(x) (x).begin(), (x).end()
#define alll(x) (x), (x) + n
#define clr(x) (x).clear();
#define fri(x) for(int i = 0; i < x; ++i)
#define frj(x) for(int j = 0; j < x; ++j)
#define frp(x) for(int p = 0; p < x; ++p)
#define frr(a, b) for(int i = a; i < b; ++i)
#define frrj(a, b) for(int j = a; j < b; ++j)
#define fra(x) for(int i = 0; i < x; ++i) cin >> a[i];
#define frb(x) for(int i = 0; i < x; ++i) cin >> b[i];
#define frs(x) for(auto it = x.begin(); it != x.end(); ++it)
#define fr(x) for(auto it : x) //el
#define fastio ios_base::sync_with_stdio(false); cin.tie(0);
#define dbg(x) cerr << #x << ": " << x << endl;
#define ce(x) cout << x << endl;
#define uniq(x) x.resize(unique(all(x)) - x.begin()); //make all one after sorting
#define blt __builtin_popcount
/////////////////////print array, vector, deque, set, multiset, pair, map /////////////////////
void print(long long t) {cerr << t;}
void print(int t) {cerr << t;}
void print(string t) {cerr << t;}
void print(char t) {cerr << t;}
void print(double t) {cerr << t;}
void print(long double t) {cerr << t;}
void print(unsigned long long t) {cerr << t;}
template <class T, class V> void print(pair <T, V> p) {cerr << "{"; print(p.first); cerr << ","; print(p.second); cerr << "}";}
template <class T, class V> void print(T v[],V n) {cerr << "["; for(int i = 0; i < n; i++) {print(v[i]); cerr << " "; } cerr << "]"; cout << endl;}
template <class T> void print(vector <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]"; cout << endl;}
template <class T> void print(set <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]"; cout << endl;}
template <class T> void print(multiset <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]"; cout << endl;}
template <class T> void print(stack <T> v) {cerr << "[ "; stack<T> s = v; while(s.size()) {T i = s.top(); print(i); s.pop(); cerr << " ";} cerr << "]"; cout << endl;}
template <class T> void print(queue <T> v) {cerr << "[ "; queue<T> s = v; while(s.size()) {T i = s.front(); print(i); s.pop(); cerr << " ";} cerr << "]"; cout << endl;}
template <class T> void print(deque <T> v) {cerr << "[ "; deque<T> s = v; while(s.size()) {T i = s.front(); print(i); s.pop_front(); cerr << " ";} cerr << "]"; cout << endl;}
template <class T, class V> void print(map <T, V> v) {cerr << "[ "; for (auto i : v) {print(i); cerr << " ";} cerr << "]"; cout << endl;}
template <class T, class V> void print(unordered_map <T, V> v) {cerr << "[ "; for (auto i : v) {print(i); cerr << " ";} cerr << "]"; cout << endl;}
/////////////////////code/////////////////////
int a[200005];
int main() {
fastio;
int n, s; cin >> n >> s; fra(n)
vpi ans;
if(s == 2) {
int m = n;
for(int i = 19; i >= 0; i--) {
bool f = 0;
frj(m - 1) {
if(a[j] & (1 << i)) {
f = 1;
if(a[j + 1] & (1 << i)) {
ans.pb({j, j + 1});
a[j] ^= a[j + 1];
}
else {
ans.pb({j + 1, j});
ans.pb({j, j + 1});
a[j + 1] ^= a[j];
a[j] ^= a[j + 1];
}
}
}
if(f) m--;
}
} else {
int last = 0;
for (int i = n-1; i > 0; --i) { //esqan hatvacy der sortac chi
int idx = 0;
for (int j = 0; j <= i; ++j) //gtn amenamec ^last ov id n (lasty verjin tivna vorov sax xor enq arel)
if ((a[j] ^ last) > (a[idx] ^ last))
idx = j;
//idx(c) y tanelu enq verj
for(int j = 0; j <= min(i, n-2); j++) { //stananq a^b b^c c^d...f
ans.pb(mp(j, j + 1));
a[j] = (a[j] ^ a[j + 1]);
}
for (int j = idx + 1; j <= i; ++j) { //stananq a^b b^c c^d c^e c^f c
ans.pb(mp(j, j - 1));
a[j] = (a[j] ^ a[j - 1]);
}
for (int j = idx - 1; j > 0; --j) { //stananq c^a c^b c^d c^e c^f c
ans.pb(mp(j - 1, j));
a[j - 1] = (a[j - 1] ^ a[j]);
}
last = a[i]; //misht c^a c^b c^d c^e c^f c tesqi a linelu, dra hamar hajord amenamecy gtnelu hamar last=c vor xor anenq
}
ans.pb(mp(0, 1));
a[0] = (a[0] ^ a[1]); //vor taky amenapoqr elem y mna
}
//ent c^a c^b c^d c^e c^f ic heto piti d n berenq verj
//1in qaylov darav a^b b^d d^e e^f f inchpes naxord qaylum ev sharunakutyuny nuynn e
//a^b b^d d^e d^f d -> a^d b^d d^e d^f d ev ayln
cout << ans.size() << endl;
for(pii p : ans)
cout << p.ff + 1 << ' ' << p.ss + 1 << endl;
return 0;
}
// ♥ ♥ ♥ ♥ ♥ ♥ ♥ ♥
// ♥ ♥ ♥ ♥ ♥ ♥ ♥
// ♥ ♥ ♥ ♥ ♥ ♥ ♥ ♥
// ♥ ♥ ♥ ♥ ♥ ♥ ♥ ♥
// ♥ ♥ ♥ ♥ ♥ ♥ ♥ ♥
//
// God loves Fil, Fil accepts God's will
