// https://dashoj.com/p/77

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

struct g {
    ll m; // 重量
    ll u; // 价值
    double x; // 每一重的价值
};

ll n, t;
vector<g> gs;

int main() {
    cin >> n >> t;
    for (int i = 0; i < n; i++) {
        ll m, u;
        cin >> m >> u;
        gs.push_back({m, u});
        gs[i].x = (double) u / (double) m;
    }
    sort(gs.begin(), gs.end(), [](g a, g b) {
        return a.x > b.x; // 按价值 / 重量从大到小排序
    });
    double ans = 0; // 答案
    for (int i = 0; i < n; ++i) {
        if (t >= gs[i].m) {
            t -= gs[i].m;
            ans += gs[i].u;
        } else {
            ans += t * gs[i].x;
            break;
        }
    }
    printf("%.2lf", ans);
    return 0;
}