/in/foo.c: In function 'main':
/in/foo.c:14:14: warning: implicit declaration of function 'sqrt' [-Wimplicit-function-declaration]
   for (; j <=sqrt(x); j++)
              ^~~~
/in/foo.c:14:14: warning: incompatible implicit declaration of built-in function 'sqrt'
/in/foo.c:14:14: note: include '<math.h>' or provide a declaration of 'sqrt'
/in/foo.c:39:1: error: expected declaration or statement at end of input
 }
 ^