#include<iostream>
#define cn(a); \
		cin>>a;
#define ct(a); \
		cout<<a;
#define ll \
		long long
#define r; \
		return 0;
using namespace std;
ll cnt=1;
void series(int n){
	if(n==1){
		return;
	}
	cnt+=n/2;
	for(int i=1;i<=n/2;i++){
		series(i);
	}
}
int main(){
	int n;
	scanf("%d",&n);
	if(n%2==0){
		series(n);
	}else{
		series(n-1);
	}
	printf("%lld",cnt);
	re;
}

超时25！！