#include <bits/stdc++.h>
using namespace std;
double n;
double s;
double f;
double bfb;
int main(){
    cin>>n;
    s=(n*n)*1.0;
    f=(2*n-1+4)*1.0;
//    cout<<f<<" "<<s;
    bfb=f*1.0/s*1.0;
    printf("%.1f",bfb);
    cout<<"%";
	return 0;
}
/**************************************************************
	Problem: 1345
	User: zengdongxin
	Language: C++
	Result: Wrong Answer
****************************************************************/