#include<iostream>
#include<cstdio>
#include<vector>
#define N 3000
#define M 20
#define K 100000
#define inf 1e9
using namespace std;
int read()
{
	char c=0;
	int sum=0;
	while (c<'0'||c>'9') c=getchar();
	while ('0'<=c&&c<='9') sum=sum*10+c-'0',c=getchar();
	return sum;
}
struct reads
{
	int x,y;
};
reads tong[K+1];
int n,k,length,F[N+1],F2[N+1],dp[M+1][N+1],ps[M+1][N+1];
void adder(int x,int y)
{
	tong[++length]=(reads){x-1,y-1};
	return;
}
void solve(int l,int r)
{
	if (r-l<=k) return;
	int res=r-l+1;
	vector<int>s(n+2);
	vector<int>used(n+2);
	vector<int>p(k);
	for (int i=k;i>=1;--i)
	{
		res=ps[i][res];
		if (i!=1) p[i-1]=res+l,s[p[i-1]]=used[p[i-1]]=1;
	}
	for (int i=l;i<=r;++i) s[i]+=s[i-1];
	for (int i=1;i<=k-2;++i)
		if (p[i+1]-p[i]>1)
			adder(p[i],p[i+1]);
	for (int i=l;i<=r;++i)
		if (!used[i])
		{
			if (s[i]&&i-p[s[i]]>1) adder(p[s[i]],i);
			if (s[i]!=k-1&&p[s[i]+1]-i>1) adder(i,p[s[i]+1]);
		}
	if (l<=p[1]-1) solve(l,p[1]-1);
	for (int i=1;i<=k-2;++i)
		if (p[i]+1<=p[i+1]-1)
			solve(p[i]+1,p[i+1]-1);
	if (p[k-1]+1<=r) solve(p[k-1]+1,r);
	return;
}
int main()
{
	n=read(),k=read();
	for (int i=1;i<=k;++i)
		for (int j=0;j<=n+1;++j)
			dp[i][j]=inf;
	for (int i=0;i<=n;++i) F[i]=max(i-1,0),F2[i]=max(i-1,0)<<1;
	for (int i=1;i<=n+1;++i)
	{
		if (i<=k+1) dp[1][i]=0;
		else
		{
			for (int j=2;j<=k;++j)
			{
				if (j==2)
				{
					if (k==2)
					{
						for (int t=0;t<=i-1;++t)
							if (dp[j-1][t]+dp[1][i-1-t]+F[t]+F[i-1-t]<dp[j][i])
								dp[j][i]=dp[j-1][t]+dp[1][i-1-t]+F[t]+F[i-1-t],ps[j][i]=t;
					}
					else
					{
						for (int t=0;t<=i-1;++t)
							if (dp[j-1][t]+dp[1][i-1-t]+F[t]+F2[i-1-t]<dp[j][i])
								dp[j][i]=dp[j-1][t]+dp[1][i-1-t]+F[t]+F2[i-1-t],ps[j][i]=t;
					}
				}
				else if (j==k)
				{
					for (int t=0;t<=i-1;++t)
						if (dp[j-1][t]+dp[1][i-1-t]+F[i-1-t]+(t!=i-1)<dp[j][i])
							dp[j][i]=dp[j-1][t]+dp[1][i-1-t]+F[i-1-t]+(t!=i-1),ps[j][i]=t;
				}
				else
				{
					for (int t=0;t<=i-1;++t)
						if (dp[j-1][t]+dp[1][i-1-t]+F2[i-1-t]+(t!=i-1)<dp[j][i])
							dp[j][i]=dp[j-1][t]+dp[1][i-1-t]+F2[i-1-t]+(t!=i-1),ps[j][i]=t;
				}
			}
			dp[1][i]=dp[k][i];
		}
	}
	solve(1,n+1),printf("%d\n",length);
	for (int i=1;i<=length;++i) printf("%d %d\n",tong[i].x,tong[i].y);
	return 0;
}