#include <bits/stdc++.h>
using namespace std;
    vector<vector<int> > ans;
    int k;
int f[1005];
int from[1005];
void solve(int l,int r) {
    if(r-l+1 == k) {
        vector<int> cur;
        for(int j = l;j <= r;j++) cur.push_back(j) ;
        ans.push_back(cur) ; return ;
    }
    int u = from[r - l + 1] ;
    int len = (r - l + 1) / u;
    for(int i = l ; i <= r ;i += len) {
        solve(i , i + len - 1);
    }
    for(int dl = 0 , dr;dl < len; dl = dr + 1) {
        vector<int> cur ;
        dr = dl + k/u - 1;
        for(int i = dl ; i <= dr ; i++) {
            for(int j = l + i ; j <= r ; j += len) cur.push_back(j);
        }
        ans.push_back(cur);
    }
    return ;
}
int main() {
    int n;cin >> n >> k;
    vector<int> v;
    for(int i = 2;i <= k;i++) {
        if(k % i == 0) v.push_back(i) ;
    }
    f[k] = 1;
    for(int i = k + 1;i <= n;i++) {
        for(auto u : v) {
            if(i % u == 0 && f[i / u]) {f[i] = 1 ; from[i] = u ; break ;}
        }
    }
    if(!f[n]) {
        cout << -1 ; return 0;
    }
    solve(1 , n);
    cout << ans.size() << '\n';
    for(auto v : ans) {
        for(auto x : v) cout << x <<' ' ;
        cout << '\n';
    }
}