#include<bits/stdc++.h>
using namespace std;
int main(){
    float n,z;
    cin>>n;
    if(n>15){
        z=(n-15)/2.5+10;
    }else{
        z=n/1.5;
    }
    printf("%.2f",z);
    return 0;
}
/**************************************************************
	Problem: 1052
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/