#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	double y,e,p;
	cin>>n;
	y=n*0.8;
	e=n*0.9;
	p=(n+y+e)/3;
	printf("%.1f",p);
}

/**************************************************************
	Problem: 1613
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/