#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ll mask){return __builtin_ctzll(mask);}
int logOf(ll mask){return __lg(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T& container, string separator = " ", string finish = "\n"){
for(auto item: container) cout << item << separator;
cout << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const int INF = 1e9 + 69;
int n, k;
vector<pair<int, int>> a;
pair<double, int> alien_shyt(int m, int lambda){
pair<double, int> dp[n+1][m+1];
for(int i = 0; i <= n; ++i) for(int j = 0; j <= m; ++j) dp[i][j] = {INF, 0};
dp[0][0] = {0, 0};
for(int i = 0; i < n; ++i) for(int j = 0; j <= m; ++j){
pair<double, int> cur = dp[i][j];
if (j < m){
pair<double, int> _cur = make_pair(cur.first + (double)a[i].second / (j+1), cur.second);
minimize(dp[i+1][j+1], _cur);
}
if (a[i].first <= lambda){
pair<double, int> _cur = make_pair(cur.first + (double)(a[i].first - lambda) / (m+1), cur.second - 1);
minimize(dp[i+1][j], _cur);
}
else{
minimize(dp[i+1][j], cur);
}
}
return make_pair(dp[n][m].first, -dp[n][m].second);
}
void solve(){
cin >> n >> k;
a.resize(n);
for(int i = 0; i < n; ++i) {
cin >> a[i].first >> a[i].second;
if (a[i].second == -1) a[i].second = 1e6;
}
sort(ALL(a), [](pair<int, int> x, pair<int, int> y){return x.second < y.second;});
double ans = 1e18;
int r = 1000;
for(int i = 0; i < k; ++i){ // we will use i helpers
while(r > 0){
pair<double, int> cuh = alien_shyt(i, r-1);
if (cuh.second < k - i) break;
r--;
}
pair<double, int> cuh = alien_shyt(i, r);
minimize(ans, cuh.first + (double)(r * (k - i)) / (i + 1));
}
cout << fixed << setprecision(10) << ans << "\n";
}
int main(void){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << "ms!\n";
return 0;
}
