#include <stdio.h>
#include <algorithm>
using namespace std;
#define ll long long
#define LIM 100111
#define MAXANS 1e10
#define EPS 1e-5

struct line {
    // y = mx + b
    double m, b;
    double intercept(double y) {
        return (y - b) / m;
    }
};


int pos[LIM];
int bago[LIM];
int orig[LIM];
line lines[LIM];
double intercept[LIM];
int n;


ll inversions() {
    for (int i = 0; i < n; i++) bago[i] = pos[bago[i]];

    // number of inversions in 'bago'
    #define fenwick orig
    for (int i = 0; i <= n; i++) fenwick[i] = 0;
    ll ans = 0;
    for (int i = n-1; i >= 0; i--) {
        for (int v = bago[i]+1; v; v ^= v & -v) {
            ans += fenwick[v];
        }
        for (int v = bago[i]+1; v <= n; v += v & -v) {
            fenwick[v]++;
        }
    }
    return ans;
    #undef fenwick
}

bool comp(int i, int j) {
    return intercept[i] < intercept[j];
}
void get_order(int *indices, double y) {
    // get order of intercepts at the line "y = y"
    for (int i = 0; i < n; i++) {
        intercept[i] = lines[i].intercept(y);
    }
    sort(indices, indices + n, comp);
}

int main() {
    ll k;
    scanf("%d%lld", &n, &k);
    for (int i = 0; i < n; i++) {
        scanf("%lf%lf", &lines[i].m, &lines[i].b);
        bago[i] = orig[i] = i;
    }

    get_order(orig, -MAXANS);
    for (int i = 0; i < n; i++) pos[orig[i]] = i;

    double L = -MAXANS, R = +MAXANS;
    while (R - L > EPS) {
        double M = 0.5 * (L + R);
        get_order(bago, M);
        (inversions() < k ? L : R) = M;
    }
    printf("%.11lf\n", L);
}