样例过了，在Codeforces里面WA了第二个点

#include <bits/stdc++.h>
#define int long long
#define iostream() ios::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
using namespace std;
const int maxn = 1e6+7;
const int MAXN = maxn / 2;
signed main()
{
    iostream();
    int n;
    cin >> n;
    string s;
    cin >> s;
    s = " " + s;
    if (n % 2 == 0)
    {
    	for (int i = 1; i <= n; i++)
    	{
    		if (i % 2 == 0 && i != n)
    			cout << s[i] << '-';
    		else
    			cout << s[i];
		}
		cout << '\n';
	}
	else if (n % 3 == 0)
	{
		for (int i = 1; i <= n; i++)
    	{
    		if (i % 3 == 0 && i != n)
    			cout << s[i] << '-';
    		else
    			cout << s[i];
		}
		cout << '\n';
	}
	else
	{
		int tmp = 1,fn = n;
		while (n > 3)
		{
			for (int i = 1; i <= 2; i++)
	    	{
	    		if (i % 2 == 0)
	    			cout << s[i] << '-';
	    		else
	    			cout << s[i];
	    		tmp++;
			}
			n -= 2;
		}
		printf("%c%c%c",s[n - 2],s[n - 1],s[n]);
	}
 	return 0;
}