#include <bits/stdc++.h>
#include <cmath>

using namespace std;
typedef long long ll;
//typedef unsigned long long ll;

#define rep(i, n) for (int i = 0; i < (n); ++i)
//#define rep(i, n) for (ll i = 0; i < (n); ++i)
//#define sz(x) ll(x.size())
//typedef pair<ll, int> P;
//typedef pair<ll, ll> P;
//const double INF = 1e10;
//const ll INF = LONG_LONG_MAX / 10;
//const ll INF = 1e15;
const ll MINF = LONG_LONG_MIN;
const int INF = INT_MAX / 10;
#define cmin(x, y) x = min(x, y)
#define cmax(x, y) x = max(x, y)
//typedef pair<int, int> P;
typedef pair<double, double> P;

bool contain(set<P> &s, P a) { return s.find(a) != s.end(); }

//ifstream myfile("C:\\Users\\riku\\Downloads\\0_00.txt");
//ofstream outfile("log.txt");
//outfile << setw(6) << setfill('0') << prefecture << setw(6) << setfill('0') << rank << endl;
// std::cout << std::bitset<8>(9);


void print_line(vector<int> &line) {
    if (line.size() == 0ll) {
        cout << endl;
        return;
    }
    for (ll i = 0; i < line.size(); i++) {
        cout << line[i];
        if (i == line.size() - 1) cout << endl;
        else cout << ' ';
    }
}


typedef priority_queue<long long, vector<long long>, greater<long long>> PQ_ASK;
const int mod = 1000000007;

int main() {

    int n;
    double w;
    cin >> n >> w;

    vector<P> items(n);
    rep(i, n) cin >> items[i].first >> items[i].second;

    sort(items.begin(), items.end(), [](P p, P q) {
        return p.first / p.second > q.first / q.second;
    });

    double sum_weight = 0;
    double sum_value = 0;

    rep(i, n) {
        double nokori = w - sum_weight;
        P p = items[i];
        if (nokori >= p.second) {
            sum_weight += p.second;
            sum_value += p.first;
        } else {
            sum_weight += nokori;
            sum_value += (p.first / p.second) * nokori;
        }
    }

    printf("%.20f\n", sum_value);

}
