求问怎么在外面加上如图的图表框框！
https://img-mid.csdnimg.cn/release/static/image/mid/ask/684658482566192.jpeg
#include<stdio.h>
int main()
{
int i,j,result;
printf("\n");
for (i=1;i<10;i++)
{
for(j=1;j<=i;j++)
{
result=ij;
printf("%d%d=%-3d",i,j,result); /-3d表示左对齐，占3位/
}
printf("\n"); /每一行后换行/
}
}