#include <iostream>
#include <iomanip>

int main() {
    int n;
    std::cin >> n;
    int total_area = n * n;
    // 计算中间行和中间列的粉色玫瑰数量，减去中间重复计算的一个
    int pink_area = 2 * n - 1;
    // 加上四个顶点的粉色玫瑰数量
    pink_area += 3;
    double percentage = (static_cast<double>(pink_area) / total_area) * 100;
    std::cout << std::fixed << std::setprecision(1) << percentage << "%" << std::endl;
    return 0;
}    
/**************************************************************
	Problem: 1345
	User: linmiaoling
	Language: C++
	Result: Wrong Answer
****************************************************************/