Error(s):

source_file.c: In function ‘main’:
source_file.c:7:15: warning: initialization makes integer from pointer without a cast [-Wint-conversion]
     char sign="-";
               ^
source_file.c:11:12: error: expected ‘(’ before ‘sign’
         if sign=-{
            ^
source_file.c:18:1: error: expected declaration or statement at end of input
 }
 ^
source_file.c:7:10: warning: variable ‘sign’ set but not used [-Wunused-but-set-variable]
     char sign="-";
          ^