/in/foo.c: In function 'main':
/in/foo.c:20:24: warning: statement with no effect [-Wunused-value]
   20 |         else(a!=0&&b!=0&&b*b-4*a*c<0)
      |             ~~~~~~~~~~~^~~~~~~~~~~~~~
/in/foo.c:20:38: error: expected ';' before 'printf'
   20 |         else(a!=0&&b!=0&&b*b-4*a*c<0)
      |                                      ^
      |                                      ;
   21 |                 printf("方程无解”）；
      |                 ~~~~~~                
/in/foo.c:21:24: warning: missing terminating " character
   21 |                 printf("方程无解”）；
      |                        ^
/in/foo.c:21:24: error: missing terminating " character
   21 |                 printf("方程无解”）；
      |                        ^~~~~~~~~~~~~~