#include<bits/stdc++.h>
using namespace std;
int main(){

	float ms,zs,b;
	int n ;
	//const float pi=3.14;
	cin>>n;
	zs=n*n;
	ms=n+n-1+4;
	b=ms*1.0/zs*100.0;
	printf("%.1f",b);
	cout<<'%'; 
	return 0;
}


/**************************************************************
	Problem: 1345
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/