#include<iostream>
#include<stdio.h>
#include<vector>
using namespace std;


int main()
{
	int n, t;
	double t1 = 0.0, money = 0.0;
	double avmoney = 0.0;
	cin >> n;
	cin >> t;
	double m[10005] = { 0 };
	double v[10005] = { 0 };

	for (int i = 1; i <= n; i++)
	{
		cin >> m[i];
		cin >> v[i];
	}
	for (int i = 1; i <= n; i++)
	{
		if (t1 + m[i] <= t)
		{
			t1 = t1 + m[i];
			money = money + v[i];
		}
		else
		{
			avmoney = v[i] / m[i];
			money = ((t - t1) * avmoney) + money;
			break;
		}
	}
	printf("%.2lf", (double)money);
	return 0;
}