#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
#define op(x) ((x&1)?x+1:x-1)
#define odd(x) (x&1)
#define even(x) (!odd(x))
#define lc(x) (x<<1)
#define rc(x) (lc(x)|1)
#define lowbit(x) (x&-x)
#define mp(x,y) make_pair(x,y)
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
using namespace std;
const int MAXN = 2010,MAXK = 20,INF = 1e8;

int n,k,f[MAXK][MAXN],pf[MAXK][MAXN],g[MAXK][MAXN],pg[MAXK][MAXN];

typedef array<int,2> pr;
vector<pr> ret;

void link(int x,int y){
	assert(y-x>1);
	ret.push_back({x,y});
}
void out(){
	cout<<ret.size()<<"\n";
	for(auto [x,y] : ret)cout<<x-1<<" "<<y-1<<"\n";
}

void cmin(int& f,int& p,int vf,int vp){
	if(vf<f){
		f = vf;
		p = vp;
	}
}

int Fp(int k,int n){
	if(n<=1)return 0;
	return f[k][n-1] + (n-2);
}
int Fs(int k,int n){
	if(n<=1)return 0;
	return f[k][n] + (n-1);
}
int Fps(int k,int n){
	if(n<=1)return 0;
	return f[k][n-1] + (2*n-3);
}

void calc(int k,int n){
	f[k][n] = INF;
	rep(i,1,n/2){ //两侧的块大小
		int cost = g[k][n-2*i] + Fs(k,i) + Fp(k,i);
		cmin(f[k][n],pf[k][n],cost,i);
		if(n-2*i>0){
			int cost = g[k][n-2*i-1] + Fs(k,i) + Fp(k,i+1);
			cmin(f[k][n],pf[k][n],cost,-i);
		}
	}
}
void _calc(int k,int n){
	g[k][n] = INF;
	rep(i,1,n){ //块的总数
		int cost = f[k-2][i+1] + Fps(k,n/i)*(i-n%i) + Fps(k,n/i+1)*(n%i);
		cmin(g[k][n],pg[k][n],cost,i);
	}
}

int arr[MAXN];

void solve(const int*,int,int);
void _solve(const int*,int,int);
void sp(const int*,int,int);
void ss(const int*,int,int);
void spf(const int*,int,int);

int main(){
	//freopen("matrix.in","r",stdin);
	//freopen("matrix.out","w",stdout);

	cin>>n>>k; n++;

	rep(i,3,n)f[1][i] = (i-2)*(i-1)/2;
	rep(i,4,n){
		int mid = (i+1)/2;
		f[2][i] = f[2][mid-1] + f[2][i-mid] + (i-3);
	}
	//
	rep(j,3,k){
		rep(i,1,n){
			if(i>=j+2)calc(j,i);
			_calc(j,i);
		}
	}

	rep(i,1,n)arr[i] = i;

	solve(arr,k,n);

	out();
    return 0;
}
void sp(const int* arr,int k,int n){
	if(n<=1)return;
	solve(arr+1,k,n-1);
	rep(i,3,n)link(arr[1],arr[i]);
}
void ss(const int* arr,int k,int n){
	if(n<=1)return;
	solve(arr,k,n);
	rep(i,1,n-1)link(arr[i],arr[n+1]);
}
void spf(const int* arr,int k,int n){
	if(n<=1)return;
	solve(arr+1,k,n-1);
	rep(i,3,n)link(arr[1],arr[i]);
	rep(i,1,n-1)link(arr[i],arr[n+1]);
}

void _solve(const int* arr,int k,int n){
	assert(n); int i = pg[k][n];
	int cnt = n%i; //前cnt个的长度是n/i+1，后i-cnt个的长度是n/i
	int tmp[MAXN],tot=0; 
	for(int p=1,cur=0,len=0;cur<i;p+=len,cur++){
		len=n/i+(cur<cnt); 
		spf(arr+p-1,k,len);
		tmp[++tot] = arr[p];
	}	
	tmp[++tot] = arr[n+1];
	solve(tmp,k-2,tot);
}

void solve(const int* arr,int k,int n){
	if(n <= k+1)return;
	if(k==1){
		rep(i,1,n)rep(j,i+2,n)link(arr[i],arr[j]);
		return;
	}else if(k==2){
		int mid = (n+1)/2;
		solve(arr,k,mid-1);
		solve(arr+mid,k,n-mid);
		rep(i,1,mid-2)link(arr[i],arr[mid]);
		rep(i,mid+2,n)link(arr[mid],arr[i]);
		return;
	}
	int i = abs(pf[k][n]),tag = (pf[k][n] < 0);
	ss(arr,k,i); sp(arr+n-i-tag,k,i + tag);
	_solve(arr+i,k,n-2*i-tag);
}