zadnji

#include <iostream>
using namespace std;

int main() {
	int N = 0;
	cout << "Upisite N :D \n";
	cin >> N;

	float pi = 0;
	float multi = 1;

	for(int i = 0; i < N ; ++i, multi += 2)
		i % 2 == 0 ? pi += (1/multi) : pi -= (1/multi);

	pi *= 4;
	cout << pi;
	return 0;
}