#include <iostream>
#include <iomanip>

int main() {
    int n;
    std::cin >> n;

    int total = n * n;
    int pink = 2 * n + 2 - 3;

    double ratio = static_cast<double>(pink) / total * 100;

    std::cout << std::fixed << std::setprecision(1) << ratio << '%' << std::endl;

    return 0;
}    
/**************************************************************
	Problem: 1345
	User: fuyijun
	Language: C++
	Result: Wrong Answer
****************************************************************/