#include <bits/pthreadtypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <stdbool.h>

#ifdef __PROGTEST__
#define debug(...) ((void)0)
#else
#define debug(fmt, ...) fprintf(stdout, "[%s:%d %s()] " fmt "\n", __FILE__, __LINE__, __func__, ##__VA_ARGS__)
#endif

// https://www.geeksforgeeks.org/dsa/area-of-intersection-of-two-circles/
double intersection_area(double a_r, double b_r, double distance) {
	double a_square = a_r * a_r;
	double b_square = b_r * b_r;
	double distane_square = distance * distance;

	double alpha = acos((distane_square + a_square - b_square) / (2 * a_r * distance)) * 2;
	double beta = acos((distane_square + b_square - a_square) / (2 * b_r * distance)) * 2;

	double a1 = 0.5 * beta * b_square - 0.5 * b_square * sin(beta);
	double a2 = 0.5 * alpha * a_square - 0.5 * a_square * sin(alpha);

	double area = a1 + a2;

	debug("Area = %lf", area);

	return area;
}

double circle_area(double radius) {
	return M_PI * radius * radius;
}

int main() {
	double a_center_x = 0, a_center_y = 0, a_radius = 0, b_center_x = 0, b_center_y = 0, b_radius = 0;

	printf("Zadejte parametry kruznice #1:\n");

	int inputs_read = scanf("%lf %lf %lf", &a_center_x, &a_center_y, &a_radius);
	if(inputs_read != 3 || a_radius <= 0) {
		printf("Nespravny vstup.\n");
		return EXIT_FAILURE;
	}

	printf("Zadejte parametry kruznice #2:\n");

	inputs_read = scanf("%lf %lf %lf", &b_center_x, &b_center_y, &b_radius);
	if(inputs_read != 3 || b_radius <= 0) {
		printf("Nespravny vstup.\n");
		return EXIT_FAILURE;
	}


	double center_distance = sqrt((b_center_x - a_center_x) * (b_center_x - a_center_x) + (b_center_y - a_center_y) * (b_center_y - a_center_y));

	double radii_sum = a_radius + b_radius;
	if(a_center_x == b_center_x && a_center_y == b_center_y && a_radius == b_radius) {
		printf("Kruznice splyvaji, prekryv: %lf\n", circle_area(a_radius));
	} else if(center_distance <= a_radius - b_radius) {
		debug("B radius = %lf", b_radius);
		debug("Double A radius = %lf", a_radius * 2);
		if(a_radius == 2 * b_radius) {
			printf("Vnitrni dotyk, kruznice #2 lezi uvnitr kruznice #1, prekryv: %lf\n", circle_area(b_radius));
		} else {
			printf("Kruznice #2 lezi uvnitr kruznice #1, prekryv: %lf\n", circle_area(b_radius));
		}
	} else if(center_distance <= b_radius - a_radius) {
		debug("A radius = %lf", a_radius);
		debug("Double B radius = %lf", b_radius * 2);
		if(b_radius == 2 * a_radius) {
			printf("Vnitrni dotyk, kruznice #1 lezi uvnitr kruznice #2, prekryv: %lf\n", circle_area(a_radius));
		} else {
			printf("Kruznice #1 lezi uvnitr kruznice #2, prekryv: %lf\n", circle_area(a_radius));
		}
	} else if(center_distance < radii_sum) {
		printf("Kruznice se protinaji, prekryv: %lf\n", intersection_area(a_radius, b_radius, center_distance));
	} else if(center_distance == radii_sum) {
		printf("Vnejsi dotyk, zadny prekryv.\n");
	} else {
		printf("Kruznice lezi vne sebe, zadny prekryv.\n");
	}

	return EXIT_SUCCESS;
}