#include<bits/stdc++.h>
using namespace std;
struct me {
    double y, sum,d;
} mi[101];
bool cmp(me a, me b) {
    return a.d  > b.d ;
}
int main() {
    int n, m;
    cin >> m >> n;
    for (int i = 1; i <= m; i++) {
        cin >> mi[i].y >> mi[i].sum;
        mi[i].d=mi[i].y / mi[i].sum;
    }
    sort(mi + 1, mi + m + 1, cmp);
    double  s = 0, r = n;
    for (int i = 1; i <= m; i++) {
        if (r >= mi[i].sum) {
            s += mi[i].y;
            r -= mi[i].sum;
        } else {
            s += mi[i].d * r;
            r = 0;
            break;
        }
    }
    printf("%.2lf", s);
    return 0;
}