PROGRAM Prime_numbers
   IMPLICIT NONE
   INTEGER, ALLOCATABLE, DIMENSION(:) :: Prime
   INTEGER :: N_elts, i ,j
   
   PRINT*, "Type in the size of the array"
   READ*, N_elts
   ALLOCATE (Prime(N_elts), STAT=i)
   IF (i.NE.0) THEN
      PRINT*, "Allocation request failed"
      STOP
   ENDIF
   
   Prime = (/ (i, i = 1,N_elts) /)
   i = 2
   outa : DO
      DO j=i+1,N_elts
         IF (MOD(Prime(j),i).EQ.0) Prime(j) = 0
      ENDDO
      DO 
         i = i + 1
         IF (i .EQ. N_elts) EXIT outa
         IF (Prime(i) .NE. 0) EXIT
      END DO
   END DO outa
   DO i = 1, N_elts
      IF (Prime(i) .NE. 0) WRITE(*,*) Prime(i)
   END DO
   DEALLOCATE(Prime)
   STOP
END PROGRAM Prime_Numbers