#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: wengsihan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/