/in/foo.c: In function 'main':
/in/foo.c:7:19: error: expected expression before 'double'
    7 |   for(i=sqrt(sqrt(double(a)));i<=sqrt(double(a));i++){
      |                   ^~~~~~
/in/foo.c:7:39: error: expected expression before 'double'
    7 |   for(i=sqrt(sqrt(double(a)));i<=sqrt(double(a));i++){
      |                                       ^~~~~~