Calm Down Light Oj

#include<stdio.h>
#include<string.h>
#include<math.h>
#define pi acos(-1)

int main() {
    int t, c=1;
    double R, r, z, n;
    scanf("%d", &t);
    while(t--) {
        scanf("%lf %lf", &R, &n);
        z=sin(pi/n);
        r=(R*z)/(1+z);
        printf("Case %d: %lf\n", c++, r);
    }
    return 0;
}