#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;

typedef double real;

const int N = 10005;
const real eps = 1e-8;

inline real sqr(real x) { return x*x; }

int n, q;
real x[N], y[N], xba, yba, xss, yss, lxx, lxy, lyy;

real get_Q(int s, int m) {
	if(fabs(lxy) < eps) {
		if(fabs(lxx-lyy) < eps) return lxx / (n+m-1);
		else return lyy / (n+m-1);
	}
	real p = lxx-lyy, q = 2*lxy*lxy;
	real delta = sqrt(sqr(p)+2*q);
	real Q = (lxx+lyy - delta)/2;
	return Q / (n+m-1);
}

real gao(int s, int m) {
	int n1 = n+m-1;
	xba = 0, yba = 0;
	lxx = 0, lxy = 0, lyy = 0;
	for(int i = 0; i < n; ++i) {
		int k = i == s ? m : 1;
		xba += k*x[i];
		yba += k*y[i];
		lxx += k*x[i]*x[i];
		lyy += k*y[i]*y[i];
		lxy += k*x[i]*y[i];
	}
	lxx -= xba*xba/n1;
	lyy -= yba*yba/n1;
	lxy -= xba*yba/n1;
	xba /= n1;
	yba /= n1;
	if(fabs(lxx) < eps) {
		return 0.0;
	} else {
		return get_Q(s, m);
	}
}

const real K = 1e-3;

int main() {
	for(int cas = 1; 2==scanf("%d%d", &n, &q) && n; ++cas) {
		for(int i = 0; i < n; ++i) {
			scanf("%lf%lf", x+i, y+i);
		}
		printf("Case %d:\n", cas);
		printf("%.5f\n", gao(0, 1));
		for(int s, m, i = 1; i <= q; ++i) {
			scanf("%d%d", &s, &m);
			printf("%d: %.5f\n", i, gao(s, m));
		}
	}
}