/*
primen.c
find largest prime less than or equal to target
use djb primegen library ("atkin's sieve")
wcm, 2004.02.19 - 2004.02.19
===
*/
#include <stdlib.h>
#include <stdio.h>

#include <primegen.h>

int
main(int argc, char **argv)
{
  primegen  pg;
  uint64    target = 0L;
  uint64    last = 0L;

  if(argv[1])
      target = strtoull(argv[1],NULL,10);
  if(target < 2)
      exit(EXIT_FAILURE);

  primegen_init(&pg);

  while(primegen_peek(&pg) <= target)
      last = primegen_next(&pg);

  printf("%llu\n", last);

  return 0;
}

/* that's all, folks! */