#include <stdio.h>
int main(void){
	int L;
	long int count = 0;
	int moji;
	
	scanf("%d",&L);
	
	for(int odd = L; odd >= 3; odd -= 2){
		moji = L;
		while(moji >= odd){
			count++;
			moji -= 2;
		}
	}
	for(int even = L-1; even >= 3; even -= 2){
		moji = L-1;
		while(moji >= even){
			count++;
			moji -= 2;
		}
	}
	printf("%ld\n",count);
	
	return 0;
}