#!/usr/bin/env python3
#coding:utf-8

import math
import string
import random
from sys import stdin
# import numpy as np
# from matplotlib import pyplot as plt
	

def main():
	read=stdin.readline

	#edit here!
	n,k=map(int,read().split())
	i=2
	ans=1
	while i*i<=n :
		if n%i==0:
			if ans<(i//2)*(n//i):
				ans=(i//2)*(n//i)
		i+=1
	print(ans)




if __name__ == '__main__':
	main()