#include <stdio.h>
#include <stdlib.h>
#define EPSINON  1e-3
#define ABS(a)  (((a)>0)?(a):(-a)) //？：不支持表達式嵌套
#define ZERO(x)  ((x)>-EPSINON && (x)<EPSINON)
#define MAX(a,b) (((a)>(b))?(a):(b))
#define MIN(a,b) (((a)<(b))?(a):(b))
float a, b, c;
float max, mid, min;
char input_err_flag = 0;
char judge_err_flag = 0;
int equal(float a, float b)
{
 float tmp;
 tmp = a - b;
 tmp = ZERO(ABS(tmp));
 return tmp;
}
void input(void)
{
 a = b = c = 0;
 printf("輸入三條邊的值：");
 scanf("%f %f %f",&a, &b, &c);
 if(!(a>0) || !(b>0) || !(c>0))
 {
  input_err_flag = 1;
 }
}
void sort(void)
{
 max = MAX(MAX(a,b),c);
 min = MIN(MIN(a,b),c);
 if(MAX(a,b) < c)
  mid = MAX(a,b);
 else
  mid = MAX(MIN(a,b),c);
}
void judge(void)
{
 float max_square, mid_square, min_square, tmp;
 if(max >= (mid+min))
 {
  judge_err_flag = 1;
 }
 else
 {
  max_square = max * max;
  mid_square = mid * mid;
  min_square = min * min;
  tmp = mid_square + min_square;
  if(equal(mid,min) || equal(max, mid))
  {
   if(equal(mid, min))
   {
    if(mid == max)
     puts("等邊三角形。");
    else if(equal(max_square, tmp))
     puts("等腰直角三角形。");
    else if(max_square < tmp)
     puts("等腰銳角三角形。");
    else
     puts("等腰鈍角三角形。");
   }
   else
   {
    if(equal(min, mid))
     puts("等邊三角形。");
    else
     puts("等腰銳角三角形。");
   }
  }
  else if(equal(max_square, tmp))
   puts("直角三角形。");
  else if(max_square < tmp)
   puts("銳角三角形。");
  else
   puts("鈍角三角形。");
 }
}
int main(void)
{
 char cs, ch;
 do
 {
  input();
  sort();
  judge();
  if(input_err_flag)
  {
   input_err_flag = 0;
   while((cs=getchar())!='/n' && (cs=getchar())!=EOF);
   printf("輸入錯誤，a b c必須大于零，是否新輸入(y/n)：");
  }
  else if(judge_err_flag)
  {
   judge_err_flag = 0;
   while((cs=getchar())!='/n' && (cs=getchar())!=EOF);
   printf("組不成三角形,是否重新輸入(y/n)：");
  }
  else
  {
   while((cs=getchar())!='/n' && (cs=getchar())!=EOF);
   printf("是否再輸入一組數據(y/n)：");
  }
  ch = getchar();
 }
 while(ch=='y' || ch=='Y' || ch=='/n');
 puts("Goodbye!");
 return 0;
}