Help me in solving PRIMEPERM problem

help
,
1

My issue

plz give me hint…

My code

#include <bits/stdc++.h>
using namespace std;

int main() {
	// your code goes here
	int t;
	cin>>t;
	int n;
	while(t--){
	    cin>>n;
	    if(n<4) cout<<"-1"<<endl;
	    if()
	}
	return 0;
}

Problem Link: PRIMEPERM Problem - CodeChef

2

include <bits/stdc++.h>
using namespace std;

bool is_prime(int num) {
if (num <= 1) return false;
if (num <= 3) return true;

if (num % 2 == 0 || num % 3 == 0) return false;

for (int i = 5; i * i <= num; i += 6) {
    if (num % i == 0 || num % (i + 2) == 0) return false;
}

return true;

}

int main() {
int t;
cin >> t;

while (t--) {
    int n;
    cin >> n;

    if (n < 4) {
        cout << "-1" << endl;
    } else {
        vector<int> permutation;
        for (int i = n; i >= 1; i--) {
            if (is_prime(i)) {
                permutation.push_back(i);
            }
        }

        if (permutation.size() >= 3) {
            swap(permutation[0], permutation[1]);
            swap(permutation[1], permutation[2]);
        }

        for (int num : permutation) {
            cout << num << " ";
        }
        cout << endl;
    }
}

return 0;

}