#include "stdio.h"
void add(bianchang)
{int i,j,c;
 c=bianchang;
 for(i=1;i<=c;i=i++)
 {for(j=1;j<=c;j=j++)
  {if(i==1||i==c)
  printf("*");
  else {if(j==1||j==c)
  printf("*");
  else printf(" ");}}
   printf("\n");
}}
void main()
{int n;
 printf("input bianchang please:");
 scanf("%d",&n);
 while(n>0)
 {
  add(n);
  printf("input bianchag please:");
  scanf("%d",&n);}}