Error(s):

source_file.c: In function ‘fun’:
source_file.c:27:1: error: expected declaration specifiers before ‘return’
 return 0;
 ^
source_file.c:28:1: error: expected declaration specifiers before ‘}’ token
 }
 ^
source_file.c:28:1: error: expected ‘{’ at end of input
source_file.c: In function ‘main’:
source_file.c:28:1: error: expected declaration or statement at end of input
source_file.c:25:1: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d",&start,&end);
 ^