/in/foo.c: In function 'main':
/in/foo.c:16:5: error: 'else' without a previous 'if'
   16 |     else if(d==0)
      |     ^~~~
/in/foo.c:20:9: error: 'else' without a previous 'if'
   20 |         else{e=-b/2/a;f=sqrt(-d)/2/a;
      |         ^~~~
/in/foo.c:20:14: error: 'e' undeclared (first use in this function)
   20 |         else{e=-b/2/a;f=sqrt(-d)/2/a;
      |              ^
/in/foo.c:20:14: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:20:23: error: 'f' undeclared (first use in this function)
   20 |         else{e=-b/2/a;f=sqrt(-d)/2/a;
      |                       ^
/in/foo.c:8:8: warning: unused variable 'i' [-Wunused-variable]
    8 |   char i;
      |        ^