Problem:
Score : 100 points

Problem Statement

Print the circumference of a circle of radius R.

Constraints

1 \leq R \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

R

Output

Print the circumference of the circle.
Your output is considered correct if and only if its absolute or relative error from our answer is at most 10^{-2}.

Sample Input 1

1

Sample Output 1

6.28318530717958623200

Since we accept an absolute or relative error of at most 10^{-2}, 6.28 is also an acceptable output, but 6 is not.

Sample Input 2

73

Sample Output 2

458.67252742410977361942

Solution in C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>

int main(void) {
	int n, m, i;
	int a[1000000];

	scanf("%d%d", &n, &m);

	for (i = 0; i < m; i++) {
		scanf("%d", &a[i]);
	}

	for (i = 0; i < m; i++) {
		n -= a[i];
		if (n < 0) {
			printf("-1\n");
			return 0;
		}
	}

	printf("%d\n", n);

	return 0;
}