小弟刚学c＋＋，做练习碰到下面问题，麻烦大家帮我看看，最后输出没结果，大家帮我看看，感激不尽！！
编写一个打印正方形的程序，例如，读取一个数5，谈后输出如下
× × × × ×
×          ×
×          ×
×          ×
× × × × ×
下面是我的程序：
# include < iostream.h >

int main ()
{
    int m, n, i ;
    
    cout << "lenth is :" ;
    cin >> m ;

    if ( m==1 )
        cout << "* " << endl ;
    else
    {
        for ( n=1; n<=m; n++ )
        {    if ( n==1 && n==m )
            {
                for (n=1; n<=m; n++)
                    cout << "* " ;
                cout << '\n' ;
            }

            else
            {
                for( i=1; i<=m; i++)
                {
                    if ( n==1 && n==m )
                        cout << "* " ;
                    else cout << "  " ;
                    
                    cout << '\n' ;
                }

            }
        }
    }
}