import java.util.Scanner;
public class Main
{
public static void main
(String[] args
) {
int n, powOf2 = 1;
double x, sum = 0;
Scanner scanner
= new Scanner
(System.
in);
n = scanner.nextInt();
x = scanner.nextDouble();
for (int i = 1; i <= n; i++)
{
powOf2 *= 2;
sum
+= Math.
sin(i
*x
)/powOf2
; }
}
}
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