i'm cant pass few test cases although i have followed what you said. help?

    int n;
    cin >> n;
    if(n < 3 || n == 4 || n == 7)
    {
        cout << -1 << endl;
        continue;
    }
    if(n == 8)
    {
        cout << "55533333" << endl;
        continue;
    }

    if(n%3 == 0)
    {
        for(int i = 0; i < n; i++)
            cout << "5";
        cout << endl;
    }
    else if(n%5 == 0)
    {
        for(int i = 0; i < n; i++)
            cout << "3";
        cout << endl;
    }
    else if(n%3 == 2)
    {
        for(int i = 0; i < n-5; i++)
            cout << "5";
        for(int i = n - 5; i < n; i++)
            cout << "3";
        cout << endl;
    }
    else if(n%3 == 1)
    {
        for(int i = 0; i < n-10; i++)
            cout << "5";
        for(int i = n-10; i < n; i++)
            cout << "3";
        cout << endl;
    }
    else
        cout << -1 << endl;