1002.c

#include <stdio.h>
#include <stdlib.h>

int main() {

	double r = 0, pi = 3.14159;

	char buffer[100];

	fgets(buffer, 100, stdin);
	r = strtod(buffer, NULL);

	printf("A=%.4f\n",  pi * (r * r));

	return 0;
}