k-String codeforces

#include <bits/stdc++.h>
using namespace std;
 
int main()
{
	string a,b,c;
	int n;
	cin>>n>>a;
	sort(a.begin(),a.end());
	for(int i=0;i<a.size();i+=n)
        b+=a[i];
	for(int i=0;i<n;i++)
	c+=b;
	b=c;
	sort(b.begin(),b.end());
	if(b!=a) 
        cout<<-1;
	else 
	cout<<c;
	return 0;
}