#include <cstdio>
#include <cmath>

int n, q;
double x[10005], y[10005];

double gao(int s, int m) {
	int num = n+m-1;
	double 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];
		lxy += k*x[i]*y[i];
		lyy += k*y[i]*y[i];
	}
	lxx -= xba*xba/num;
	lxy -= xba*yba/num;
	lyy -= yba*yba/num;
	double p = lxx-lyy, q = 2*lxy;
	double delta = sqrt(p*p+q*q);
	double Q = (lxx+lyy-delta)/2;
	return Q/num;
}

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));
		}
	}
}