#include<iostream>
#include<cstring>
#include<algorithm>
#include<iomanip>
using namespace std;

int main()
{
	int N, T;
	cin >> N >> T;
	double m[101], v[101];
	for (int i = 0;i < N;i++) {
		cin >> m[i] >> v[i];
	}
	double avg[2][101]={0};
	for (int i = 0;i < N;i++)
	{
		avg[0][i] = v[i] / m[i];
		avg[1][i] = m[i];
	}

	sort(avg[0], avg[0] + N, greater<double>());

	double sum=0;
	for (int i = 0;i<N;i++)
	{
		if (T > avg[1][i]) { sum += avg[0][i] * avg[1][i];T -= avg[1][i]; }
		else { sum += avg[0][i] * T;break; }
	}
	cout << fixed <<setprecision(2) << sum << endl;
}