#include <iostream>
using namespace std;

# define PI           3.1415926

double currentPow = 1;
int currentPowIndex = 0;
double currentFactNumber = 1;
int currentFactNumberIndex = 0;

double cached_pow(double number, int powIndex) {
    for (int i = currentPowIndex; i < powIndex; i++) {
        currentPow *= number;
    }

    currentPowIndex = powIndex;
    return currentPow;
}

double cached_fact (int factNumberIndex) {
    for (int i = factNumberIndex; i > currentFactNumberIndex; i--) {
        currentFactNumber *= i;
    }

    currentFactNumberIndex = factNumberIndex;
    return currentFactNumber;
}

int main() {
    double x = 120.0 / 180.0 * PI;
    double sinx = x;
    int sign = 1;
    double nextValue = 0.0;
    //877 iterations
    for (int i = 1; 0 != (nextValue = (cached_pow(x, 2*i + 1) / cached_fact(2*i + 1))); i++) {
        sign *= -1;
        sinx += sign * nextValue;
    }

    cout << sinx << endl;

	return 0;
}