#include<iostream>
#include<cstdio>
#include<vector>
#include<cmath>
#define N 1000000
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[N+1];
int n,k,length,st[N+1],leng;
void adder(int x,int y)
{
	tong[++length]=(reads){x,y};
	return;
}
int main()
{
	int ps=0,rst;
	n=read(),k=read();
	while (1)
	{
		rst=1;
		for (int i=1;i<=k;++i) rst=min(rst*ps,n-1);
		if (rst>=n-1) break;
		ps++;
	}
	for (int i=1;i<=n-1;i*=ps)
		for (int j=1;j<=ps-1;++j)
			for (int k=1;k+i*j<=n;++k)
				if (i*j!=1)
					adder(k,k+i*j);
	printf("%d\n",length);
	for (int i=1;i<=length;++i) printf("%d %d\n",tong[i].x,tong[i].y);
	return 0;
}