#include <iostream>
#include <iomanip>
using namespace std;
   
int main() {
    int n;
    cin >> n;
      
    // 计算粉玫瑰格数 
    int pink = 2 * n + 3;
      
    // 计算百分比 
    double percentage = (double)pink / (n * n) * 100;
      
    // 输出结果，保留1位小数 
    cout << fixed << setprecision(1) << percentage << "%";
      
    return 0;
/**************************************************************
	Problem: 1345
	User: baizhoudeyueguang
	Language: C++
	Result: Compile Error
****************************************************************/