#include <bits/stdc++.h>
using namespace std;
int main(){
   int x; 
   float c=0,v=0,b=0;
   cin>>x;
   c=x*0.8;
   v=x*0.9;
   b=(x+c+v)/3.0;
   printf("%.1f",b); 
}
   
   
   
   
   
   
   
   
   
   
   
   
    



/**************************************************************
	Problem: 1613
	User: binzicheng1
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/