#include<bits/stdc++.h>
using namespace std;
int main(){
	int a;
	float p;
	scanf("%d",&a);
	if (a>10){
		p=(a+2.5*10)/4.0;
		printf("%.2f",p);
	}
	else {
		p=a/1.5;
		printf("%.2f",p);
	}
	return 0;
}
/**************************************************************
	Problem: 1052
	User: xiaojingxuan
	Language: C++
	Result: Wrong Answer
****************************************************************/