#include <bits/stdc++.h>
using namespace std;
int m[105], v[105];

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