#include<bits/stdc++.h>
using namespace std;
int main() {
	int x;
	float i=0,j=0,h=0;
	cin>>x;
	i=x*0.8;
	j=x*0.9;
	h=(x+i+j)/3;
	printf("%.1f",h);
    return 0;
}
/**************************************************************
	Problem: 1613
	User: linzihang
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/