题解 | 小红的不动点构造

#include <bits/stdc++.h>

using namespace std;
using i64 = int64_t;
//typedef long long ll;
//#define int long long //signed

void solve(){
    int n,m;
    cin >> n >> m;
    if(n-m == 1) cout << -1 << endl;
    else{
    	for(int i = 1; i <= m; i++){
    		cout << i << " ";
    	}
        int cnt = m;
    	for(int i = n; i > m; i--){
            cnt++;
            if(cnt == i) {
                cout << i-1 << " " << i << " ";
                i--;
                cnt = -INT_MAX;
                continue;
            }
            cout << i << " ";
    	}
    	cout << endl;
    	
    }
}
    
int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t = 1;
    //std::cin >> t;
    while(t--){
        solve();
    }
  
    return 0;
}