和机器人跳跃问题(找的是左端点)是一样的，二分找右端点即可

import java.util.*;

public class Main {
    static final int N = 100010;
    static int[] h = new int[N], w = new int[N];
    static int n, m;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String[] s = sc.nextLine().split(" ");
        n = Integer.parseInt(s[0]); m = Integer.parseInt(s[1]);

        for (int i = 0; i < n; i++) {
            String[] str = sc.nextLine().split(" ");
            h[i] = Integer.parseInt(str[0]);
            w[i] = Integer.parseInt(str[1]);
        }

        int l = 1, r = 100000;
        while (l < r) {
            int mid = l + r + 1 >> 1;
            if (cheek(mid)) l = mid;
            else r = mid - 1;
        }

        System.out.println(l);
    }

    static boolean cheek(int u) {
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            cnt += (h[i] / u) * (w[i] / u);
            if (cnt >= m) return true;   
        }
        return false;
    }
}