gpa____#define

// Problem: gpa
// Contest: NowCoder
// URL: https://ac.nowcoder.com/acm/contest/22353/T
// Memory Limit: 524288 MB
// Time Limit: 2000 ms
// 2022-04-30 11:32:20
// 
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
using namespace std;

#define rep(i,l,r) for(int i=(l);i<=(r);i++)
#define per(i,l,r) for(int i=(l);i>=(r);i--)
#define ll long long
#define mset(s,t) memset(s,t,sizeof(t))
#define mcpy(s,t) memcpy(s,t,sizeof(t))
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define mp make_pair

typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;   
typedef vector<ll> Vll;               
typedef vector<pair<int, int> > vpii;
typedef vector<pair<ll, ll> > vpll;                        

const ll mod = 1e9 + 7;
//const ll mod = 998244353;
const double pi  = acos(-1.0);
inline ll ksc(ll x,ll y,ll mod)
{
    ll ans = 0;
    while (y) {
        if (y & 1)
            ans = (ans + x) %mod;
        y >>= 1;
        x = (x + x) %mod;
    }
    return ans;
}
inline ll qmi (ll a, ll b) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans = ans * a;
        a = a * a;
        b >>= 1;
    }
    return ans;
}
inline int read () {
    int x = 0, f = 0;
    char ch = getchar();
    while (!isdigit(ch)) f |= (ch=='-'),ch= getchar();
    while (isdigit(ch)) x = x * 10 + ch - '0', ch = getchar();
    return f?-x:x;
}
template<typename T> void print(T x) {
    if (x < 0) putchar('-'), x = -x;
    if (x >= 10) print(x/10);
    putchar(x % 10 + '0');
}
inline ll sub (ll a, ll b) {
    return ((a - b ) %mod + mod) %mod;
}
inline ll add (ll a, ll b) {
    return (a + b) %mod;
}
// inline ll inv (ll a) {
    // return qmi(a, mod - 2);
// }
const int N = 1e5 +10;
int n, k;
double c[N], s[N];
double b[N];
bool check(double tar) {
    for (int i = 1; i <= n;i  ++)
        b[i] = s[i] * c[i] - tar * s[i];
    sort(b + 1, b + 1 + n);
    double ans = 0;
    int id = k + 1;
    for (int i = 1; i <= k; i ++) {
        if (b[i] >= 0) {
            id = i;
            break;
        }
    }
    for (int i = id; i <= n;i  ++)
        ans += b[i];
    if (ans >= 0) return 1;
    return 0;
}
void solve() {
    cin >> n >> k;
    for (int i = 1; i <= n; i ++)
        cin >> s[i];
    for (int i = 1; i <= n; i ++) {
        cin >> c[i];
    }
    double l = 0, r = 1e10;
    for (int i = 0; i <= 100; i ++) {
        double mid = (l + r) /2;
        if (check(mid)) l = mid;
        else r = mid;
    }
    printf("%.12lf\n", l);
}
int main () {
    // ios::sync_with_stdio(0),cin.tie(0), cout.tie(0);
    int t;
    t =1;
    //cin >> t;
    while (t --) solve();
    return 0;
}