//
//  Created by fpdjsns
//  Copyright © 2019 fpdjsns. All rights reserved.
//

/*
 * 시간복잡도 : O(N)
 */

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

int main() {
	int t;
	cin >> t;
	for (int c = 1; c <= t; c++) {

		int D, N, K, S;
		cin >> D >> N;

		double maxHours = 0;
		for (int i = 0; i < N; i++) {
			cin >> K >> S;
			maxHours = max(maxHours, (double)(D - K) / S);
		}

		printf("Case #%d: %lf\n", c, D / maxHours);
	}

	return 0;
}