#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: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/