/in/foo.c: In function 'main':
/in/foo.c:6:2: error: 'a' undeclared (first use in this function)
  a[10000]={0};
  ^
/in/foo.c:6:2: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:11: error: expected expression before '{' token
  a[10000]={0};
           ^
/in/foo.c:14:6: error: 'i' undeclared (first use in this function)
  for(i=2;i<n;i++)
      ^