Miscellany

#include <iostream>
#include <vector>
#define _USE_MATH_DEFINES
#include <math.h>
#include <string>

using namespace std;

int main ()
{
	double aireTotale = 0.0;
	vector<double> angles;

	string lol;

	for(;;) {
		cin >> lol;
		if (lol == "$") {
			break;
		}

		double a = atof(lol.c_str());
		angles.push_back(a * M_PI);
	}

	for (int i = 0; i < angles.size() - 1; i++)
	{
		double angleTotal = angles[i + 1] - angles[i];

		aireTotale += sin(angleTotal) / 2;
	}

	// The last one
	double angleTotal = (2*M_PI + angles[0]) - angles[angles.size() - 1];
	aireTotale += sin(angleTotal) / 2;

	printf("%.2f", aireTotale);

	return 0;
}