C++ :

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <vector>

using namespace std;

const int MAXN = 100000 + 1000;

typedef pair<int, int> pii;
typedef pair<long long, int> pli;

int n;
long long m;
int px[MAXN], py[MAXN], xx[MAXN];
int s[MAXN];

int lowbit(int x)
{
	return x & (-x);
}
void clear()
{
	memset(s, 0, sizeof(s));
	return ;
}
void modify(int x, int v)
{
	for(int i = x; i; i -= lowbit(i))
		s[i] += v;
	return ;
}
int query(int x)
{
	int ret = 0;
	for(int i = x; i <= n; i += lowbit(i))
		ret += s[i];
	return ret;
}

void init()
{
	static pii arr[MAXN];
	for(int i = 1; i <= n; i++)
		arr[i] = make_pair(px[i], i);
	sort(arr + 1, arr + n + 1);
	int tot = 1;
	xx[arr[1].second] = tot;
	for(int i = 2; i <= n; i++)
		tot += (arr[i].first != arr[i - 1].first), xx[arr[i].second] = tot;
	return ;
}

long long calc(int k)
{
	static pli arr[MAXN];
	long long ret = 0;
	for(int i = 1; i <= n; i++)
		arr[i] = make_pair(py[i] - (long long)k * px[i], xx[i]);
	sort(arr + 1, arr + n + 1, greater<pli>());
	clear();
	for(int i = 1; i <= n; i++)
		ret += query(arr[i].second + 1), modify(arr[i].second, 1);
	return ret;
}

int main()
{
	ios::sync_with_stdio(false);
//	freopen("slope.in", "r", stdin);
//	freopen("slope.out", "w", stdout);
	cin >> n >> m;
	for(int i = 1; i <= n; i++)
		cin >> px[i] >> py[i];
	init();
	int l = -210000000, r = 210000000;
	while(l < r)
	{
		int mid = (l + r + 1) / 2;
		if(calc(mid) >= m)
			l = mid;
		else
			r = mid - 1;
	}
	int ans = l;
	cout << ans << endl;

	return 0;
}