PROgram IS_PRIME

implicit none


integer:: i
real::sqrti
integer::counter=1

read(*,*) i

if(i==2) then
 print *,"prime"
else if(i==1 .or. mod(i,2)==0) then
 print *,"not prime2"
else
 sqrti=sqrt(real(i))
 do
  counter = counter +1
  if(mod(i,counter)==0) then
   print *, "not prime1",counter
   exit
  end if
  if(counter>sqrti) then
   print *,"is prime"
   exit
  end if
 end do


end if

end program IS_PRIME